printk from NMI context relies on irq work being raised on the local CPU
to print to console. This can be a problem if the NMI was raised by a
lockup detector to print lockup stack and regs, because the CPU may not
enable irqs (because it is locked up).
Introduce printk_trigger_flush() that can be called another CPU to try
to get those messages to the console, call that where printk_safe_flush
was previously called.
Fixes: 93d102f094 ("printk: remove safe buffers")
Cc: stable@vger.kernel.org # 5.15
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211107045116.1754411-1-npiggin@gmail.com
Merge misc updates from Andrew Morton:
"257 patches.
Subsystems affected by this patch series: scripts, ocfs2, vfs, and
mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
cleanups, kfence, and damon)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
mm/damon: remove return value from before_terminate callback
mm/damon: fix a few spelling mistakes in comments and a pr_debug message
mm/damon: simplify stop mechanism
Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
Docs/admin-guide/mm/damon/start: simplify the content
Docs/admin-guide/mm/damon/start: fix a wrong link
Docs/admin-guide/mm/damon/start: fix wrong example commands
mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
mm/damon: remove unnecessary variable initialization
Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
selftests/damon: support watermarks
mm/damon/dbgfs: support watermarks
mm/damon/schemes: activate schemes based on a watermarks mechanism
tools/selftests/damon: update for regions prioritization of schemes
mm/damon/dbgfs: support prioritization weights
mm/damon/vaddr,paddr: support pageout prioritization
mm/damon/schemes: prioritize regions within the quotas
mm/damon/selftests: support schemes quotas
mm/damon/dbgfs: support quotas of schemes
...
Rename memblock_free_ptr() to memblock_free() and use memblock_free()
when freeing a virtual pointer so that memblock_free() will be a
counterpart of memblock_alloc()
The callers are updated with the below semantic patch and manual
addition of (void *) casting to pointers that are represented by
unsigned long variables.
@@
identifier vaddr;
expression size;
@@
(
- memblock_phys_free(__pa(vaddr), size);
+ memblock_free(vaddr, size);
|
- memblock_free_ptr(vaddr, size);
+ memblock_free(vaddr, size);
)
[sfr@canb.auug.org.au: fixup]
Link: https://lkml.kernel.org/r/20211018192940.3d1d532f@canb.auug.org.au
Link: https://lkml.kernel.org/r/20210930185031.18648-7-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Juergen Gross <jgross@suse.com>
Cc: Shahab Vahedi <Shahab.Vahedi@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'printk-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Extend %pGp print format to print hex value of the page flags
- Use kvmalloc instead of kmalloc to allocate devkmsg buffers
- Misc cleanup and warning fixes
* tag 'printk-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
vsprintf: Update %pGp documentation about that it prints hex value
lib/vsprintf.c: Amend static asserts for format specifier flags
vsprintf: Make %pGp print the hex value
test_printf: Append strings more efficiently
test_printf: Remove custom appending of '|'
test_printf: Remove separate page_flags variable
test_printf: Make pft array const
ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG_PRINTK
printk: use gnu_printf format attribute for printk_sprint()
printk: avoid -Wsometimes-uninitialized warning
printk: use kvmalloc instead of kmalloc for devkmsg_user
Fix the following W=1 kernel build warning:
kernel/printk/printk.c: In function 'printk_sprint':
kernel/printk/printk.c:1913:9: warning: function 'printk_sprint' might be
a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210927142203.124730-1-john.ogness@linutronix.de
clang notices that the pi_get_entry() function would use
uninitialized data if it was called with a non-NULL module
pointer on a kernel that does not support modules:
kernel/printk/index.c:32:6: error: variable 'nr_entries' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
if (!mod) {
^~~~
kernel/printk/index.c:38:13: note: uninitialized use occurs here
if (pos >= nr_entries)
^~~~~~~~~~
kernel/printk/index.c:32:2: note: remove the 'if' if its condition is always true
if (!mod) {
Rework the condition to make it clear to the compiler that we are always
in the second case. Unfortunately the #ifdef is still required as the
definition of 'struct module' is hidden when modules are disabled.
Fixes: 3370155737 ("printk: Userspace format indexing support")
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210928093456.2438109-1-arnd@kernel.org
The boot-time allocation interface for memblock is a mess, with
'memblock_alloc()' returning a virtual pointer, but then you are
supposed to free it with 'memblock_free()' that takes a _physical_
address.
Not only is that all kinds of strange and illogical, but it actually
causes bugs, when people then use it like a normal allocation function,
and it fails spectacularly on a NULL pointer:
https://lore.kernel.org/all/20210912140820.GD25450@xsang-OptiPlex-9020/
or just random memory corruption if the debug checks don't catch it:
https://lore.kernel.org/all/61ab2d0c-3313-aaab-514c-e15b7aa054a0@suse.cz/
I really don't want to apply patches that treat the symptoms, when the
fundamental cause is this horribly confusing interface.
I started out looking at just automating a sane replacement sequence,
but because of this mix or virtual and physical addresses, and because
people have used the "__pa()" macro that can take either a regular
kernel pointer, or just the raw "unsigned long" address, it's all quite
messy.
So this just introduces a new saner interface for freeing a virtual
address that was allocated using 'memblock_alloc()', and that was kept
as a regular kernel pointer. And then it converts a couple of users
that are obvious and easy to test, including the 'xbc_nodes' case in
lib/bootconfig.c that caused problems.
Reported-by: kernel test robot <oliver.sang@intel.com>
Fixes: 40caa127f3 ("init: bootconfig: Remove all bootconfig data when the init memory is removed")
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If CONFIG_MODULES is n, we got this:
kernel/printk/index.c:146:13: warning: ‘pi_remove_file’ defined but not used [-Wunused-function]
Move it inside #ifdef block to fix this warning.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210804130105.18732-1-yuehaibing@huawei.com
console_verbose() increases console loglevel to
CONSOLE_LOGLEVEL_MOTORMOUTH, which provides more information
to debug a panic/oops.
Unfortunately, in Arista we maintain some DUTs (Device Under Test) that
are configured to have 9600 baud rate. While verbose console messages
have their value to post-analyze crashes, on such setup they:
- may prevent panic/oops messages being printed
- take too long to flush on console resulting in watchdog reboot
In all our setups we use kdump which saves dmesg buffer after panic,
so in reality those extra messages on console provide no additional value,
but rather add risk of not getting to __crash_kexec().
Provide printk.console_no_auto_verbose boot parameter, which allows
to switch off printk being verbose on oops/panic/lockdep.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210727130635.675184-3-dima@arista.com
Syslog's SYSLOG_ACTION_READ is supposed to block until the next
syslog record can be read, and then it should read that record.
However, because @syslog_lock is not held between waking up and
reading the record, another reader could read the record first,
thus causing SYSLOG_ACTION_READ to return with a value of 0, never
having read _anything_.
By holding @syslog_lock between waking up and reading, it can be
guaranteed that SYSLOG_ACTION_READ blocks until it successfully
reads a syslog record (or a real error occurs).
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-7-john.ogness@linutronix.de
@syslog_lock was a raw_spin_lock to simplify the transition of
removing @logbuf_lock and the safe buffers. With that transition
complete, and since all uses of @syslog_lock are within sleepable
contexts, @syslog_lock can become a mutex.
Note that until now register_console() would disable interrupts
using irqsave, which implies that it may be called with interrupts
disabled. And indeed, there is one possible call chain on parisc
where this happens:
handle_interruption(code=1) /* High-priority machine check (HPMC) */
pdc_console_restart()
pdc_console_init_force()
register_console()
However, register_console() calls console_lock(), which might sleep.
So it has never been allowed to call register_console() from an
atomic context and the above call chain is a bug.
Note that the removal of read_syslog_seq_irq() is slightly changing
the behavior of SYSLOG_ACTION_READ by testing against a possibly
outdated @seq value. However, the value of @seq could have changed
after the test, so it is not a new window. A follow-up commit closes
this window.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-6-john.ogness@linutronix.de
All NMI contexts are handled the same as the safe context: store the
message and defer printing. There is no need to have special NMI
context tracking for this. Using in_nmi() is enough.
There are several parts of the kernel that are manually calling into
the printk NMI context tracking in order to cause general printk
deferred printing:
arch/arm/kernel/smp.c
arch/powerpc/kexec/crash.c
kernel/trace/trace.c
For arm/kernel/smp.c and powerpc/kexec/crash.c, provide a new
function pair printk_deferred_enter/exit that explicitly achieves the
same objective.
For ftrace, remove the printk context manipulation completely. It was
added in commit 03fc7f9c99 ("printk/nmi: Prevent deadlock when
accessing the main log buffer in NMI"). The purpose was to enforce
storing messages directly into the ring buffer even in NMI context.
It really should have only modified the behavior in NMI context.
There is no need for a special behavior any longer. All messages are
always stored directly now. The console deferring is handled
transparently in vprintk().
Signed-off-by: John Ogness <john.ogness@linutronix.de>
[pmladek@suse.com: Remove special handling in ftrace.c completely.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-5-john.ogness@linutronix.de
With @logbuf_lock removed, the high level printk functions for
storing messages are lockless. Messages can be stored from any
context, so there is no need for the NMI and safe buffers anymore.
Remove the NMI and safe buffers.
Although the safe buffers are removed, the NMI and safe context
tracking is still in place. In these contexts, store the message
immediately but still use irq_work to defer the console printing.
Since printk recursion tracking is in place, safe context tracking
for most of printk is not needed. Remove it. Only safe context
tracking relating to the console and console_owner locks is left
in place. This is because the console and console_owner locks are
needed for the actual printing.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-4-john.ogness@linutronix.de
Currently the printk safe buffers provide a form of recursion
protection by redirecting to the safe buffers whenever printk() is
recursively called.
In preparation for removal of the safe buffers, provide an alternate
explicit recursion protection. Recursion is limited to 3 levels
per-CPU and per-context.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-3-john.ogness@linutronix.de
Commit 3370155737 ("printk: Userspace format indexing support") turned
printk() into a macro, but left the kerneldoc comment for it with the (now)
_printk() function, resulting in this docs-build warning:
kernel/printk/printk.c:1: warning: 'printk' not found
Move the kerneldoc comment back next to the (now) macro it's meant to
describe and have the docs build find it there.
Fixes: 3370155737 ("printk: Userspace format indexing support")
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/87o8aqt7qn.fsf@meer.lwn.net
The commit 3370155737 ("printk: Userspace format indexing support")
triggered the following build failure:
kernel/printk/index.c:140:6: warning: no previous prototype for ‘pi_create_file’ [-Wmissing-prototypes]
void pi_create_file(struct module *mod)
^~~~~~~~~~~~~~
kernel/printk/index.c:146:6: warning: no previous prototype for ‘pi_remove_file’ [-Wmissing-prototypes]
void pi_remove_file(struct module *mod)
^~~~~~~~~~~~~~
Fixes: 3370155737 ("printk: Userspace format indexing support")
Reported-by: kernel test robot <lkp@intel.com>
Suggested-by: Chris Down <chris@chrisdown.name>
[pmladek@suse.com: Let the compiler decide about inlining.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/lkml/YPql089IwSpudw%2F1@alley/
We have a number of systems industry-wide that have a subset of their
functionality that works as follows:
1. Receive a message from local kmsg, serial console, or netconsole;
2. Apply a set of rules to classify the message;
3. Do something based on this classification (like scheduling a
remediation for the machine), rinse, and repeat.
As a couple of examples of places we have this implemented just inside
Facebook, although this isn't a Facebook-specific problem, we have this
inside our netconsole processing (for alarm classification), and as part
of our machine health checking. We use these messages to determine
fairly important metrics around production health, and it's important
that we get them right.
While for some kinds of issues we have counters, tracepoints, or metrics
with a stable interface which can reliably indicate the issue, in order
to react to production issues quickly we need to work with the interface
which most kernel developers naturally use when developing: printk.
Most production issues come from unexpected phenomena, and as such
usually the code in question doesn't have easily usable tracepoints or
other counters available for the specific problem being mitigated. We
have a number of lines of monitoring defence against problems in
production (host metrics, process metrics, service metrics, etc), and
where it's not feasible to reliably monitor at another level, this kind
of pragmatic netconsole monitoring is essential.
As one would expect, monitoring using printk is rather brittle for a
number of reasons -- most notably that the message might disappear
entirely in a new version of the kernel, or that the message may change
in some way that the regex or other classification methods start to
silently fail.
One factor that makes this even harder is that, under normal operation,
many of these messages are never expected to be hit. For example, there
may be a rare hardware bug which one wants to detect if it was to ever
happen again, but its recurrence is not likely or anticipated. This
precludes using something like checking whether the printk in question
was printed somewhere fleetwide recently to determine whether the
message in question is still present or not, since we don't anticipate
that it should be printed anywhere, but still need to monitor for its
future presence in the long-term.
This class of issue has happened on a number of occasions, causing
unhealthy machines with hardware issues to remain in production for
longer than ideal. As a recent example, some monitoring around
blk_update_request fell out of date and caused semi-broken machines to
remain in production for longer than would be desirable.
Searching through the codebase to find the message is also extremely
fragile, because many of the messages are further constructed beyond
their callsite (eg. btrfs_printk and other module-specific wrappers,
each with their own functionality). Even if they aren't, guessing the
format and formulation of the underlying message based on the aesthetics
of the message emitted is not a recipe for success at scale, and our
previous issues with fleetwide machine health checking demonstrate as
much.
This provides a solution to the issue of silently changed or deleted
printks: we record pointers to all printk format strings known at
compile time into a new .printk_index section, both in vmlinux and
modules. At runtime, this can then be iterated by looking at
<debugfs>/printk/index/<module>, which emits the following format, both
readable by humans and able to be parsed by machines:
$ head -1 vmlinux; shuf -n 5 vmlinux
# <level[,flags]> filename:line function "format"
<5> block/blk-settings.c:661 disk_stack_limits "%s: Warning: Device %s is misaligned\n"
<4> kernel/trace/trace.c:8296 trace_create_file "Could not create tracefs '%s' entry\n"
<6> arch/x86/kernel/hpet.c:144 _hpet_print_config "hpet: %s(%d):\n"
<6> init/do_mounts.c:605 prepare_namespace "Waiting for root device %s...\n"
<6> drivers/acpi/osl.c:1410 acpi_no_auto_serialize_setup "ACPI: auto-serialization disabled\n"
This mitigates the majority of cases where we have a highly-specific
printk which we want to match on, as we can now enumerate and check
whether the format changed or the printk callsite disappeared entirely
in userspace. This allows us to catch changes to printks we monitor
earlier and decide what to do about it before it becomes problematic.
There is no additional runtime cost for printk callers or printk itself,
and the assembly generated is exactly the same.
Signed-off-by: Chris Down <chris@chrisdown.name>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Jessica Yu <jeyu@kernel.org> # for module.{c,h}
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/e42070983637ac5e384f17fbdbe86d19c7b212a5.1623775748.git.chris@chrisdown.name
parse_prefix is needed externally by later patches, so move it into a
context where it can be used as such. Also give it the printk_ prefix to
reduce the chance of collisions.
Signed-off-by: Chris Down <chris@chrisdown.name>
Cc: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/b22ba314a860e5c7f887958f1eab2649f9bd1d06.1623775748.git.chris@chrisdown.name
In the past, `enum log_flags` was part of `struct log`, hence the name.
`struct log` has since been reworked and now this struct is stored
inside `struct printk_info`. However, the name was never updated, which
is somewhat confusing -- especially since these flags operate at the
record level rather than at the level of an abstract log.
printk_info_flags also joins its other metadata struct friends in
printk_ringbuffer.h.
Signed-off-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/3dd801982f02603e6e3aa4f8bc4f5ebb830a4949.1623775748.git.chris@chrisdown.name
The standard printk() tries to flush the message to the console
immediately. It tries to take the console lock. If the lock is
already taken then the current owner is responsible for flushing
even the new message.
There is a small race window between checking whether a new message is
available and releasing the console lock. It is solved by re-checking
the state after releasing the console lock. If the check is positive
then console_unlock() tries to take the lock again and process the new
message as well.
The commit 996e966640 ("printk: remove logbuf_lock") causes that
console_seq is not longer read atomically. As a result, the re-check might
be done with an inconsistent 64-bit index.
Solve it by using the last sequence number that has been checked under
the console lock. In the worst case, it will take the lock again only
to realized that the new message has already been proceed. But it
was possible even before.
The variable next_seq is marked as __maybe_unused to call down compiler
warning when CONFIG_PRINTK is not defined.
Fixes: commit 996e966640 ("printk: remove logbuf_lock")
Reported-by: kernel test robot <lkp@intel.com> # unused next_seq warning
Cc: stable@vger.kernel.org # 5.13
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20210702150657.26760-1-pmladek@suse.com
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Merge tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Add %pt[RT]s modifier to vsprintf(). It overrides ISO 8601 separator
by using ' ' (space). It produces "YYYY-mm-dd HH:MM:SS" instead of
"YYYY-mm-ddTHH:MM:SS".
- Correctly parse long row of numbers by sscanf() when using the field
width. Add extensive sscanf() selftest.
- Generalize re-entrant CPU lock that has already been used to
serialize dump_stack() output. It is part of the ongoing printk
rework. It will allow to remove the obsoleted printk_safe buffers and
introduce atomic consoles.
- Some code clean up and sparse warning fixes.
* tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: fix cpu lock ordering
lib/dump_stack: move cpu lock to printk.c
printk: Remove trailing semicolon in macros
random32: Fix implicit truncation warning in prandom_seed_state()
lib: test_scanf: Remove pointless use of type_min() with unsigned types
selftests: lib: Add wrapper script for test_scanf
lib: test_scanf: Add tests for sscanf number conversion
lib: vsprintf: Fix handling of number field widths in vsscanf
lib: vsprintf: scanf: Negative number must have field width > 1
usb: host: xhci-tegra: Switch to use %ptTs
nilfs2: Switch to use %ptTs
kdb: Switch to use %ptTs
lib/vsprintf: Allow to override ISO 8601 date and time separator
The cpu lock implementation uses a full memory barrier to take
the lock, but no memory barriers when releasing the lock. This
means that changes performed by a lock owner may not be seen by
the next lock owner. This may have been "good enough" for use
by dump_stack() as a serialization mechanism, but it is not
enough to provide proper protection for a critical section.
Correct this problem by using acquire/release memory barriers
for lock/unlock, respectively.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210617095051.4808-3-john.ogness@linutronix.de
dump_stack() implements its own cpu-reentrant spinning lock to
best-effort serialize stack traces in the printk log. However,
there are other functions (such as show_regs()) that can also
benefit from this serialization.
Move the cpu-reentrant spinning lock (cpu lock) into new helper
functions printk_cpu_lock_irqsave()/printk_cpu_unlock_irqrestore()
so that it is available for others as well. For !CONFIG_SMP the
cpu lock is a NOP.
Note that having multiple cpu locks in the system can easily
lead to deadlock. Code needing a cpu lock should use the
printk cpu lock, since the printk cpu lock could be acquired
from any code and any context.
Also note that it is not necessary for a cpu lock to disable
interrupts. However, in upcoming work this cpu lock will be used
for emergency tasks (for example, atomic consoles during kernel
crashes) and any interruptions while holding the cpu lock should
be avoided if possible.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
[pmladek@suse.com: Backported on top of 5.13-rc1.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210617095051.4808-2-john.ogness@linutronix.de
Commit 28e1745b9f ("printk: rename vprintk_func to vprintk") while
improving readability by removing vprintk indirection, inadvertently
placed the EXPORT_SYMBOL() for the newly renamed function at the end
of the file.
For reader sanity, and as is convention move the EXPORT_SYMBOL()
declaration just after the end of the function.
Fixes: 28e1745b9f ("printk: rename vprintk_func to vprintk")
Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210614235635.887365-1-punitagrawal@gmail.com
s/sempahore/semaphore/
s/exacly/exactly/
s/unregistred/unregistered/
s/interation/iteration/
Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
[pmladek@suse.com: Removed 4th hunk. The string has already been removed in the meantime.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210328043932.8310-1-unixbhaskar@gmail.com
The printk code is already hard enough to understand. Remove an
unnecessary indirection by renaming vprintk_func to vprintk (adding
the asmlinkage annotation), and removing the vprintk definition from
printk.c. That way, printk is implemented in terms of vprintk as one
would expect, and there's no "vprintk_func, what's that? Some function
pointer that gets set where?"
The declaration of vprintk in linux/printk.h already has the
__printf(1,0) attribute, there's no point repeating that with the
definition - it's for diagnostics in callers.
linux/printk.h already contains a static inline {return 0;} definition
of vprintk when !CONFIG_PRINTK.
Since the corresponding stub definition of vprintk_func was not marked
"static inline", any translation unit including internal.h would get a
definition of vprintk_func - it just so happens that for
!CONFIG_PRINTK, there is precisely one such TU, namely printk.c. Had
there been more, it would be a link error; now it's just a silly waste
of a few bytes of .text, which one must assume are rather precious to
anyone disabling PRINTK.
$ objdump -dr kernel/printk/printk.o
00000330 <vprintk_func>:
330: 31 c0 xor %eax,%eax
332: c3 ret
333: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
33a: 8d b6 00 00 00 00 lea 0x0(%esi),%esi
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210323144201.486050-1-linux@rasmusvillemoes.dk
Upon registering a console, safe buffers are activated when setting
up the sequence number to replay the log. However, these are already
protected by @console_sem and @syslog_lock. Remove the unnecessary
safe buffer usage.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-16-john.ogness@linutronix.de
kmsg_dump_rewind() and kmsg_dump_get_line() are lockless, so there is
no need for _nolock() variants. Remove these functions and switch all
callers of the _nolock() variants.
The functions without _nolock() were chosen because they are already
exported to kernel modules.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-15-john.ogness@linutronix.de
Since the ringbuffer is lockless, there is no need for it to be
protected by @logbuf_lock. Remove @logbuf_lock.
@console_seq, @exclusive_console_stop_seq, @console_dropped are
protected by @console_lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-14-john.ogness@linutronix.de
Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.
Update code that accesses the kernel logs using the kmsg_dumper
structure to use the new kmsg_dump_iter structure. For kmsg_dumpers,
this also means adding a call to kmsg_dump_rewind() to initialize
the iterator.
All this is in preparation for removal of @logbuf_lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org> # pstore
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-13-john.ogness@linutronix.de
All 6 kmsg_dumpers do not benefit from the @active flag:
(provide their own synchronization)
- arch/powerpc/kernel/nvram_64.c
- arch/um/kernel/kmsg_dump.c
- drivers/mtd/mtdoops.c
- fs/pstore/platform.c
(only dump on KMSG_DUMP_PANIC, which does not require
synchronization)
- arch/powerpc/platforms/powernv/opal-kmsg.c
- drivers/hv/vmbus_drv.c
The other 2 kmsg_dump users also do not rely on @active:
(hard-code @active to always be true)
- arch/powerpc/xmon/xmon.c
- kernel/debug/kdb/kdb_main.c
Therefore, @active can be removed.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-12-john.ogness@linutronix.de
The global variables @syslog_seq, @syslog_partial, @syslog_time
and write access to @clear_seq are protected by @logbuf_lock.
Once @logbuf_lock is removed, these variables will need their
own synchronization method. Introduce @syslog_lock for this
purpose.
@syslog_lock is a raw_spin_lock for now. This simplifies the
transition to removing @logbuf_lock. Once @logbuf_lock and the
safe buffers are removed, @syslog_lock can change to spin_lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-11-john.ogness@linutronix.de
@user->seq is indirectly protected by @logbuf_lock. Once @logbuf_lock
is removed, @user->seq will be no longer safe from an atomicity point
of view.
In preparation for the removal of @logbuf_lock, change it to
atomic64_t to provide this safety.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-10-john.ogness@linutronix.de
kmsg_dump_rewind_nolock() locklessly reads @clear_seq. However,
this is not done atomically. Since @clear_seq is 64-bit, this
cannot be an atomic operation for all platforms. Therefore, use
a seqcount_latch to allow readers to always read a consistent
value.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-9-john.ogness@linutronix.de
Instead of using "LOG_LINE_MAX + PREFIX_MAX" for temporary buffer
sizes, introduce CONSOLE_LOG_MAX. This represents the maximum size
that is allowed to be printed to the console for a single record.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-8-john.ogness@linutronix.de
The logic for finding records to fit into a buffer is the same for
kmsg_dump_get_buffer() and syslog_print_all(). Introduce a helper
function find_first_fitting_seq() to handle this logic.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-7-john.ogness@linutronix.de
kmsg_dump_get_buffer() requires nearly the same logic as
syslog_print_all(), but uses different variable names and
does not make use of the ringbuffer loop macros. Modify
kmsg_dump_get_buffer() so that the implementation is as similar
to syslog_print_all() as possible.
A follow-up commit will move this common logic into a
separate helper function.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-6-john.ogness@linutronix.de
The second loop of syslog_print_all() subtracts lengths that were
added in the first loop. With commit b031a684bf ("printk: remove
logbuf_lock writer-protection of ringbuffer") it is possible that
records are (over)written during syslog_print_all(). This allows the
possibility of the second loop subtracting lengths that were never
added in the first loop.
This situation can result in syslog_print_all() filling the buffer
starting from a later record, even though there may have been room
to fit the earlier record(s) as well.
Fixes: b031a684bf ("printk: remove logbuf_lock writer-protection of ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-4-john.ogness@linutronix.de
If message sizes average larger than expected (more than 32
characters), the data_ring will wrap before the desc_ring. Once the
data_ring wraps, it will start invalidating descriptors. These
invalid descriptors hang around until they are eventually recycled
when the desc_ring wraps. Readers do not care about invalid
descriptors, but they still need to iterate past them. If the
average message size is much larger than 32 characters, then there
will be many invalid descriptors preceding the valid descriptors.
The function prb_first_valid_seq() always begins at the oldest
descriptor and searches for the first valid descriptor. This can
be rather expensive for the above scenario. And, in fact, because
of its heavy usage in /dev/kmsg, there have been reports of long
delays and even RCU stalls.
For code that does not need to search from the oldest record,
replace prb_first_valid_seq() usage with prb_read_valid_*()
functions, which provide a start sequence number to search from.
Fixes: 896fbe20b4 ("printk: use the lockless ringbuffer")
Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: J. Avila <elavila@google.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210211173152.1629-1-john.ogness@linutronix.de
printk_safe_flush_on_panic() caused the following deadlock on our
server:
CPU0: CPU1:
panic rcu_dump_cpu_stacks
kdump_nmi_shootdown_cpus nmi_trigger_cpumask_backtrace
register_nmi_handler(crash_nmi_callback) printk_safe_flush
__printk_safe_flush
raw_spin_lock_irqsave(&read_lock)
// send NMI to other processors
apic_send_IPI_allbutself(NMI_VECTOR)
// NMI interrupt, dead loop
crash_nmi_callback
printk_safe_flush_on_panic
printk_safe_flush
__printk_safe_flush
// deadlock
raw_spin_lock_irqsave(&read_lock)
DEADLOCK: read_lock is taken on CPU1 and will never get released.
It happens when panic() stops a CPU by NMI while it has been in
the middle of printk_safe_flush().
Handle the lock the same way as logbuf_lock. The printk_safe buffers
are flushed only when both locks can be safely taken. It can avoid
the deadlock _in this particular case_ at expense of losing contents
of printk_safe buffers.
Note: It would actually be safe to re-init the locks when all CPUs were
stopped by NMI. But it would require passing this information
from arch-specific code. It is not worth the complexity.
Especially because logbuf_lock and printk_safe buffers have been
obsoleted by the lockless ring buffer.
Fixes: cf9b1106c8 ("printk/nmi: flush NMI messages on the system panic")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: <stable@vger.kernel.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210210034823.64867-1-songmuchun@bytedance.com
The command 'find ./kernel/printk/ | xargs ./scripts/kernel-doc -none'
reported a mismatch with the kernel-doc of prb_rec_init_wr().
Rectify the kernel-doc, such that no issues remain for ./kernel/printk/.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210125081748.19903-1-lukas.bulwahn@gmail.com
Commit f0e386ee0c ("printk: fix buffer overflow potential for
print_text()") added string termination in record_print_text().
However it used the wrong base pointer for adding the terminator.
This led to a 0-byte being written somewhere beyond the buffer.
Use the correct base pointer when adding the terminator.
Fixes: f0e386ee0c ("printk: fix buffer overflow potential for print_text()")
Reported-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210124202728.4718-1-john.ogness@linutronix.de
Before the commit 896fbe20b4 ("printk: use the lockless
ringbuffer"), msg_print_text() would only write up to size-1 bytes
into the provided buffer. Some callers expect this behavior and
append a terminator to returned string. In particular:
arch/powerpc/xmon/xmon.c:dump_log_buf()
arch/um/kernel/kmsg_dump.c:kmsg_dumper_stdout()
msg_print_text() has been replaced by record_print_text(), which
currently fills the full size of the buffer. This causes a
buffer overflow for the above callers.
Change record_print_text() so that it will only use size-1 bytes
for text data. Also, for paranoia sakes, add a terminator after
the text data.
And finally, document this behavior so that it is clear that only
size-1 bytes are used and a terminator is added.
Fixes: 896fbe20b4 ("printk: use the lockless ringbuffer")
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210114170412.4819-1-john.ogness@linutronix.de
kmsg_dump_get_buffer() uses @syslog to determine if the syslog
prefix should be written to the buffer. However, when calculating
the maximum number of records that can fit into the buffer, it
always counts the bytes from the syslog prefix.
Use @syslog when calculating the maximum number of records that can
fit into the buffer.
Fixes: e2ae715d66 ("kmsg - kmsg_dump() use iterator to receive log buffer content")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210113164413.1599-1-john.ogness@linutronix.de
Counting text lines in a record simply involves counting the number
of newline characters (+1). However, it is searching the full data
block for newline characters, even though the text data can be (and
often is) a subset of that area. Since the extra area in the data
block was never initialized, the result is that extra newlines may
be seen and counted.
Restrict newline searching to the text data length.
Fixes: b6cf8b3f33 ("printk: add lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210113144234.6545-1-john.ogness@linutronix.de
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Merge tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Finally allow parallel writes and reads into/from the lockless
ringbuffer. But it is not a complete solution. Readers are still
serialized against each other. And nested writes are still prevented
by printk_safe per-CPU buffers.
- Use ttynull as the ultimate fallback for /dev/console.
- Officially allow disabling console output by using console="" or
console=null
- A few code cleanups
* tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: remove logbuf_lock writer-protection of ringbuffer
printk: inline log_output(),log_store() in vprintk_store()
printk: remove obsolete dead assignment
printk/console: Allow to disable console output by using console="" or console=null
init/console: Use ttynull as a fallback when there is no console
printk: ringbuffer: Reference text_data_ring directly in callees.
- migrate_disable/enable() support which originates from the RT tree and
is now a prerequisite for the new preemptible kmap_local() API which aims
to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
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Merge tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- migrate_disable/enable() support which originates from the RT tree
and is now a prerequisite for the new preemptible kmap_local() API
which aims to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
* tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
sched/fair: Trivial correction of the newidle_balance() comment
sched/fair: Clear SMT siblings after determining the core is not idle
sched: Fix kernel-doc markup
x86: Print ratio freq_max/freq_base used in frequency invariance calculations
x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC
x86, sched: Calculate frequency invariance for AMD systems
irq_work: Optimize irq_work_single()
smp: Cleanup smp_call_function*()
irq_work: Cleanup
sched: Limit the amount of NUMA imbalance that can exist at fork time
sched/numa: Allow a floating imbalance between NUMA nodes
sched: Avoid unnecessary calculation of load imbalance at clone time
sched/numa: Rename nr_running and break out the magic number
sched: Make migrate_disable/enable() independent of RT
sched/topology: Condition EAS enablement on FIE support
arm64: Rebuild sched domains on invariance status changes
sched/topology,schedutil: Wrap sched domains rebuild
sched/uclamp: Allow to reset a task uclamp constraint value
sched/core: Fix typos in comments
Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug
...
Since the ringbuffer is lockless, there is no need for it to be
protected by @logbuf_lock. Remove @logbuf_lock writer-protection of
the ringbuffer. The reader-protection is not removed because some
variables, used by readers, are using @logbuf_lock for synchronization:
@syslog_seq, @syslog_time, @syslog_partial, @console_seq,
struct kmsg_dumper.
For PRINTK_NMI_DIRECT_CONTEXT_MASK, @logbuf_lock usage is not removed
because it may be used for dumper synchronization.
Without @logbuf_lock synchronization of vprintk_store() it is no
longer possible to use the single static buffer for temporarily
sprint'ing the message. Instead, use vsnprintf() to determine the
length and perform the real vscnprintf() using the area reserved from
the ringbuffer. This leads to suboptimal packing of the message data,
but will result in less wasted storage than multiple per-cpu buffers
to support lockless temporary sprint'ing.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20201209004453.17720-3-john.ogness@linutronix.de
In preparation for removing logbuf_lock, inline log_output()
and log_store() into vprintk_store(). This will simplify dealing
with the various code branches and fallbacks that are possible.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20201209004453.17720-2-john.ogness@linutronix.de
Commit 849f3127bb ("switch /dev/kmsg to ->write_iter()") refactored
devkmsg_write() and left over a dead assignment on the variable 'len'.
Hence, make clang-analyzer warns:
kernel/printk/printk.c:744:4: warning: Value stored to 'len' is never read
[clang-analyzer-deadcode.DeadStores]
len -= endp - line;
^
Simply remove this obsolete dead assignment here.
Link: https://lore.kernel.org/r/20201130124915.7573-1-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Merge tag 'printk-for-5.10-rc6-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk fixes from Petr Mladek:
- do not lose trailing newline in pr_cont() calls
- two trivial fixes for a dead store and a config description
* tag 'printk-for-5.10-rc6-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: finalize records with trailing newlines
printk: remove unneeded dead-store assignment
init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description
Any record with a trailing newline (LOG_NEWLINE flag) cannot
be continued because the newline has been stripped and will
not be visible if the message is appended. This was already
handled correctly when committing in log_output() but was
not handled correctly when committing in log_store().
Fixes: f5f022e53b ("printk: reimplement log_cont using record extension")
Link: https://lore.kernel.org/r/20201126114836.14750-1-john.ogness@linutronix.de
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Get rid of the __call_single_node union and clean up the API a little
to avoid external code relying on the structure layout as much.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
The commit 48021f9813 ("printk: handle blank console arguments
passed in.") prevented crash caused by empty console= parameter value.
Unfortunately, this value is widely used on Chromebooks to disable
the console output. The above commit caused performance regression
because the messages were pushed on slow console even though nobody
was watching it.
Use ttynull driver explicitly for console="" and console=null
parameters. It has been created for exactly this purpose.
It causes that preferred_console is set. As a result, ttySX and ttyX
are not used as a fallback. And only ttynull console gets registered by
default.
It still allows to register other consoles either by additional console=
parameters or SPCR. It prevents regression because it worked this way even
before. Also it is a sane semantic. Preventing output on all consoles
should be done another way, for example, by introducing mute_console
parameter.
Link: https://lore.kernel.org/r/20201006025935.GA597@jagdpanzerIV.localdomain
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20201111135450.11214-3-pmladek@suse.com
A bunch of functions in the new ringbuffer code take both a
printk_ringbuffer struct and a separate prb_data_ring. This is a relic
from an earlier version of the code when a second data ring was present.
Since this is no longer the case remove the extra function argument
from:
- data_make_reusable()
- data_push_tail()
- data_alloc()
- data_realloc()
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
make clang-analyzer on x86_64 defconfig caught my attention with:
kernel/printk/printk_ringbuffer.c:885:3: warning:
Value stored to 'desc' is never read [clang-analyzer-deadcode.DeadStores]
desc = to_desc(desc_ring, head_id);
^
Commit b6cf8b3f33 ("printk: add lockless ringbuffer") introduced
desc_reserve() with this unneeded dead-store assignment.
As discussed with John Ogness privately, this is probably just some minor
left-over from previous iterations of the ringbuffer implementation. So,
simply remove this unneeded dead assignment to make clang-analyzer happy.
As compilers will detect this unneeded assignment and optimize this anyway,
the resulting object code is identical before and after this change.
No functional change. No change to object code.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20201106034005.18822-1-lukas.bulwahn@gmail.com
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Merge tag 'printk-for-5.10-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk fix from Petr Mladek:
"Prevent overflow in the new lockless ringbuffer"
* tag 'printk-for-5.10-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: ringbuffer: Wrong data pointer when appending small string
Pull trivial updates from Jiri Kosina:
"The latest advances in computer science from the trivial queue"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial:
xtensa: fix Kconfig typo
spelling.txt: Remove some duplicate entries
mtd: rawnand: oxnas: cleanup/simplify code
selftests: vm: add fragment CONFIG_GUP_BENCHMARK
perf: Fix opt help text for --no-bpf-event
HID: logitech-dj: Fix spelling in comment
bootconfig: Fix kernel message mentioning CONFIG_BOOT_CONFIG
MAINTAINERS: rectify MMP SUPPORT after moving cputype.h
scif: Fix spelling of EACCES
printk: fix global comment
lib/bitmap.c: fix spello
fs: Fix missing 'bit' in comment
@setup_text_buf only copies the original text messages (without any
prefix or extended text). It only needs to be LOG_LINE_MAX in size.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200930090134.8723-3-john.ogness@linutronix.de
If a reader provides a buffer that is smaller than the message text,
the @text_len field of @info will have a value larger than the buffer
size. If readers blindly read @text_len bytes of data without
checking the size, they will read beyond their buffer.
Add this check to record_print_text() to properly recognize when such
truncation has occurred.
Add a maximum size argument to the ringbuffer function to extend
records so that records can not be created that are larger than the
buffer size of readers.
When extending records (LOG_CONT), do not extend records beyond
LOG_LINE_MAX since that is the maximum size available in the buffers
used by consoles and syslog.
Fixes: f5f022e53b ("printk: reimplement log_cont using record extension")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200930090134.8723-2-john.ogness@linutronix.de
Since there is no code that will ever store anything into the dict
ring, remove it. If any future dictionary properties are to be
added, these should be added to the struct printk_info.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200918223421.21621-4-john.ogness@linutronix.de
Dictionaries are only used for SUBSYSTEM and DEVICE properties. The
current implementation stores the property names each time they are
used. This requires more space than otherwise necessary. Also,
because the dictionary entries are currently considered optional,
it cannot be relied upon that they are always available, even if the
writer wanted to store them. These issues will increase should new
dictionary properties be introduced.
Rather than storing the subsystem and device properties in the
dict ring, introduce a struct dev_printk_info with separate fields
to store only the property values. Embed this struct within the
struct printk_info to provide guaranteed availability.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/87mu1jl6ne.fsf@jogness.linutronix.de
The majority of the size of a descriptor is taken up by meta data,
which is often not of interest to the ringbuffer (for example,
when performing state checks). Since descriptors are often
temporarily stored on the stack, keeping their size minimal will
help reduce stack pressure.
Rather than embedding the printk_info into the descriptor, create
a separate printk_info array. The index of a descriptor in the
descriptor array corresponds to the printk_info with the same
index in the printk_info array. The rules for validity of a
printk_info match the existing rules for the data blocks: the
descriptor must be in a consistent state.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200918223421.21621-2-john.ogness@linutronix.de
Use the record extending feature of the ringbuffer to implement
continuous messages. This preserves the existing continuous message
behavior.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-7-john.ogness@linutronix.de
Add support for extending the newest data block. For this, introduce
a new finalization state (desc_finalized) denoting a committed
descriptor that cannot be extended.
Until a record is finalized, a writer can reopen that record to
append new data. Reopening a record means transitioning from the
desc_committed state back to the desc_reserved state.
A writer can explicitly finalize a record if there is no intention
of extending it. Also, records are automatically finalized when a
new record is reserved. This relieves writers of needing to
explicitly finalize while also making such records available to
readers sooner. (Readers can only traverse finalized records.)
Four new memory barrier pairs are introduced. Two of them are
insignificant additions (data_realloc:A/desc_read:D and
data_realloc:A/data_push_tail:B) because they are alternate path
memory barriers that exactly match the purpose, pairing, and
context of the two existing memory barrier pairs they provide an
alternate path for. The other two new memory barrier pairs are
significant additions:
desc_reopen_last:A / _prb_commit:B - When reopening a descriptor,
ensure the state transitions back to desc_reserved before
fully trusting the descriptor data.
_prb_commit:B / desc_reserve:D - When committing a descriptor,
ensure the state transitions to desc_committed before checking
the head ID to see if the descriptor needs to be finalized.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-6-john.ogness@linutronix.de
Rather than deriving the state by evaluating bits within the flags
area of the state variable, assign the states explicit values and
set those values in the flags area. Introduce macros to make it
simple to read and write state values for the state variable.
Although the functionality is preserved, the binary representation
for the states is changed.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-5-john.ogness@linutronix.de
prb_reserve() will set some meta data values and leave others
uninitialized (or rather, containing the values of the previous
wrap). Simplify the API by always clearing out all the fields.
Only the sequence number is filled in. The caller is now
responsible for filling in the rest of the meta data fields.
In particular, for correctly filling in text and dict lengths.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-4-john.ogness@linutronix.de
Rather than continually needing to explicitly check @begin and @next
to identify a dataless block, introduce and use a BLK_DATALESS()
macro.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-3-john.ogness@linutronix.de
Move the internal get_data() function as-is above prb_reserve() so
that a later change can make use of the static function.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-2-john.ogness@linutronix.de
@state_var is copied as part of the descriptor copying via
memcpy(). This is not allowed because @state_var is an atomic type,
which in some implementations may contain a spinlock.
Avoid using memcpy() with @state_var by explicitly copying the other
fields of the descriptor. @state_var is set using atomic set
operator before returning.
Fixes: b6cf8b3f33 ("printk: add lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914094803.27365-2-john.ogness@linutronix.de
It is expected that desc_read() will always set at least the
@state_var field. However, if the descriptor is in an inconsistent
state, no fields are set.
Also, the second load of @state_var is not stored in @desc_out and
so might not match the state value that is returned.
Always set the last loaded @state_var into @desc_out, regardless of
the descriptor consistency.
Fixes: b6cf8b3f33 ("printk: add lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914094803.27365-1-john.ogness@linutronix.de
With commit 896fbe20b4 ("printk: use the lockless ringbuffer"),
printk() started silently dropping messages without text because such
records are not supported by the new printk ringbuffer.
Add support for such records.
Currently dataless records are denoted by INVALID_LPOS in order
to recognize failed prb_reserve() calls. Change the ringbuffer
to instead use two different identifiers (FAILED_LPOS and
NO_LPOS) to distinguish between failed prb_reserve() records and
successful dataless records, respectively.
Fixes: 896fbe20b4 ("printk: use the lockless ringbuffer")
Fixes: https://lkml.kernel.org/r/20200718121053.GA691245@elver.google.com
Reported-by: Marco Elver <elver@google.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200721132528.9661-1-john.ogness@linutronix.de
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Merge tag 'printk-for-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Herbert Xu made printk header file self-contained.
- Andy Shevchenko and Sergey Senozhatsky cleaned up console->setup()
error handling.
- Andy Shevchenko did some cleanups (e.g. sparse warning) in vsprintf
code.
- Minor documentation updates.
* tag 'printk-for-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
lib/vsprintf: Force type of flags value for gfp_t
lib/vsprintf: Replace custom spec to print decimals with generic one
lib/vsprintf: Replace hidden BUILD_BUG_ON() with static_assert()
printk: Make linux/printk.h self-contained
doc:kmsg: explicitly state the return value in case of SEEK_CUR
Replace HTTP links with HTTPS ones: vsprintf
hvc: unify console setup naming
console: Fix trivia typo 'change' -> 'chance'
console: Propagate error code from console ->setup()
tty: hvc: Return proper error code from console ->setup() hook
serial: sunzilog: Return proper error code from console ->setup() hook
serial: sunsab: Return proper error code from console ->setup() hook
mips: Return proper error code from console ->setup() hook
The commit 625d344978 ("Revert "kernel/printk: add kmsg SEEK_CUR
handling"") reverted a change done to the return value in case a SEEK_CUR
operation was performed for kmsg buffer based on the fact that different
userspace apps were handling the new return value (-ESPIPE) in different
ways, breaking them.
At the same time -ESPIPE was the wrong decision because kmsg /does support/
seek() but doesn't follow the "normal" behavior userspace is used to.
Because of that and also considering the time -EINVAL has been used, it was
decided to keep this way to avoid more userspace breakage.
This patch adds an official statement to the kmsg documentation pointing to
the current return value for SEEK_CUR, -EINVAL, thus userspace libraries
and apps can refer to it for a definitive guide on what to expect.
Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200710174423.10480-1-bmeneg@redhat.com
Replace the existing ringbuffer usage and implementation with
lockless ringbuffer usage. Even though the new ringbuffer does not
require locking, all existing locking is left in place. Therefore,
this change is purely replacing the underlining ringbuffer.
Changes that exist due to the ringbuffer replacement:
- The VMCOREINFO has been updated for the new structures.
- Dictionary data is now stored in a separate data buffer from the
human-readable messages. The dictionary data buffer is set to the
same size as the message buffer. Therefore, the total required
memory for both dictionary and message data is
2 * (2 ^ CONFIG_LOG_BUF_SHIFT) for the initial static buffers and
2 * log_buf_len (the kernel parameter) for the dynamic buffers.
- Record meta-data is now stored in a separate array of descriptors.
This is an additional 72 * (2 ^ (CONFIG_LOG_BUF_SHIFT - 5)) bytes
for the static array and 72 * (log_buf_len >> 5) bytes for the
dynamic array.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200709132344.760-5-john.ogness@linutronix.de
This reverts commit 3ac37a93fa.
This optimization will not apply once the transition to a lockless
printk is complete. Rather than porting this optimization through
the transition only to remove it anyway, just revert it now to
simplify the transition.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200709132344.760-4-john.ogness@linutronix.de
Introduce a multi-reader multi-writer lockless ringbuffer for storing
the kernel log messages. Readers and writers may use their API from
any context (including scheduler and NMI). This ringbuffer will make
it possible to decouple printk() callers from any context, locking,
or console constraints. It also makes it possible for readers to have
full access to the ringbuffer contents at any time and context (for
example from any panic situation).
The printk_ringbuffer is made up of 3 internal ringbuffers:
desc_ring:
A ring of descriptors. A descriptor contains all record meta data
(sequence number, timestamp, loglevel, etc.) as well as internal state
information about the record and logical positions specifying where in
the other ringbuffers the text and dictionary strings are located.
text_data_ring:
A ring of data blocks. A data block consists of an unsigned long
integer (ID) that maps to a desc_ring index followed by the text
string of the record.
dict_data_ring:
A ring of data blocks. A data block consists of an unsigned long
integer (ID) that maps to a desc_ring index followed by the dictionary
string of the record.
The internal state information of a descriptor is the key element to
allow readers and writers to locklessly synchronize access to the data.
Co-developed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200709132344.760-3-john.ogness@linutronix.de
I bet the word 'chance' has to be used in 'had a chance to be called',
but, alas, I'm not native speaker...
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200618164751.56828-7-andriy.shevchenko@linux.intel.com
Since console ->setup() hook returns meaningful error codes,
propagate it to the caller of try_enable_new_console().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200618164751.56828-6-andriy.shevchenko@linux.intel.com
This reverts commit 8ece3b3eb5.
This commit broke userspace. Bash uses ESPIPE to determine whether or
not the file should be read using "unbuffered I/O", which means reading
1 byte at a time instead of 128 bytes at a time. I used to use bash to
read through kmsg in a really quite nasty way:
while read -t 0.1 -r line 2>/dev/null || [[ $? -ne 142 ]]; do
echo "SARU $line"
done < /dev/kmsg
This will show all lines that can fit into the 128 byte buffer, and skip
lines that don't. That's pretty awful, but at least it worked.
With this change, bash now tries to do 1-byte reads, which means it
skips all the lines, which is worse than before.
Now, I don't really care very much about this, and I'm already look for
a workaround. But I did just spend an hour trying to figure out why my
scripts were broken. Either way, it makes no difference to me personally
whether this is reverted, but it might be something to consider. If you
declare that "trying to read /dev/kmsg with bash is terminally stupid
anyway," I might be inclined to agree with you. But do note that bash
uses lseek(fd, 0, SEEK_CUR)==>ESPIPE to determine whether or not it's
reading from a pipe.
Cc: Bruno Meneguele <bmeneg@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'printk-for-5.8-kdb-nmi' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk fix from Petr Mladek:
"One more printk change for 5.8: make sure that messages printed from
KDB context are redirected to KDB console handlers. It did not work
when KDB interrupted NMI or printk_safe contexts.
Arm people started hitting this problem more often recently. I forgot
to add the fix into the previous pull request by mistake"
* tag 'printk-for-5.8-kdb-nmi' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk/kdb: Redirect printk messages into kdb in any context
Petr Mladek