In (the unlikely) case our continuation merge buffer is busy, we unfortunately
can not merge further continuation printk()s into a single record and have to
store them separately, which leads to split-up output of these lines when they
are printed.
Add some flags about newlines and prefix existence to these records and try to
reconstruct the full line again, when the separated records are printed.
Reported-By: Michael Neuling <mikey@neuling.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Tested-By: Michael Neuling <mikey@neuling.org>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Restore support for partial reads of any size on /proc/kmsg, in case the
supplied read buffer is smaller than the record size.
Some people seem to think is is ia good idea to run:
$ dd if=/proc/kmsg bs=1 of=...
as a klog bridge.
Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44211
Reported-by: Jukka Ollila <jiiksteri@gmail.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We suppress printing kmsg records to the console, which are already printed
immediately while we have received their fragments.
Newly registered boot consoles print the entire kmsg buffer during
registration. Clear the console-suppress flag after we skipped the record
during its first storage, so any later print will see these records as usual.
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The /proc/kmsg read() interface is internally simply wired up to a sequence
of syslog() syscalls, which might are racy between their checks and actions,
regarding concurrency.
In the (very uncommon) case of concurrent readers of /dev/kmsg, relying on
usual O_NONBLOCK behavior, the recently introduced mutex might block an
O_NONBLOCK reader in read(), when poll() returns for it, but another process
has already read the data in the meantime. We've seen that while running
artificial test setups and tools that "fight" about /proc/kmsg data.
This restores the original /proc/kmsg behavior, where in case of concurrent
read()s, poll() might wake up but the read() syscall will just return 0 to
the caller, while another process has "stolen" the data.
This is in the general case not the expected behavior, but it is the exact
same one, that can easily be triggered with a 3.4 kernel, and some tools
might just rely on it.
The mutex is not needed, the original integrity issue which introduced it,
is in the meantime covered by:
"fill buffer with more than a single message for SYSLOG_ACTION_READ"
116e90b23f
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the recent split of facility and level into separate variables,
we miss the facility value (always 0 for kernel-originated messages)
in the syslog prefix.
On Tue, Jul 3, 2012 at 12:45 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> Static checkers complain about the impossible condition here.
>
> In 084681d14e ('printk: flush continuation lines immediately to
> console'), we changed msg->level from being a u16 to being an unsigned
> 3 bit bitfield.
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Non-printable characters in the log data are hex-escaped to ensure safe
post processing. We need to escape a backslash we find in the data, to be
able to distinguish it from a backslash we add for the escaping.
Also escape the non-printable character 127.
Thanks to Miloslav Trmac for the heads up.
Reported-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In function devkmsg_read/writev/llseek/poll/open()..., the function
raw_spin_lock/unlock is used, there is potential deadlock case happening.
CPU1: thread1 doing the cat /dev/kmsg:
raw_spin_lock(&logbuf_lock);
while (user->seq == log_next_seq) {
when thread1 run here, at this time one interrupt is coming on CPU1 and running
based on this thread,if the interrupt handle called the printk which need the
logbuf_lock spin also, it will cause deadlock.
So we should use raw_spin_lock/unlock_irq here.
Acked-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fix kernel-doc warnings in printk.c: use correct parameter name.
Warning(kernel/printk.c:2429): No description found for parameter 'buf'
Warning(kernel/printk.c:2429): Excess function parameter 'line' description in 'kmsg_dump_get_buffer'
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In reviewing Kay's fix up patch: "printk: Have printk() never buffer its
data", I found two if statements that could be combined and optimized.
Put together the two 'cont.len && cont.owner == current' if statements
into a single one, and check if we need to call cont_add(). This also
removes the unneeded double cont_flush() calls.
Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Continuation lines are buffered internally, intended to merge the
chunked printk()s into a single record, and to isolate potentially
racy continuation users from usual terminated line users.
This though, has the effect that partial lines are not printed to
the console in the moment they are emitted. In case the kernel
crashes in the meantime, the potentially interesting printed
information would never reach the consoles.
Here we share the continuation buffer with the console copy logic,
and partial lines are always immediately flushed to the available
consoles. They are still buffered internally to improve the
readability and integrity of the messages and minimize the amount
of needed record headers to store.
Signed-off-by: Kay Sievers <kay@vrfy.org>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The recent changes to the printk buffer management resulted in
SYSLOG_ACTION_READ to only return a single message, whereas previously
the buffer would get filled as much as possible. As, when too small to
fit everything, filling it to the last byte would be pretty ugly with
the new code, the patch arranges for as many messages as possible to
get returned in a single invocation. User space tools in at least all
SLES versions depend on the old behavior.
This at once addresses the issue attempted to get fixed with commit
b56a39ac26 ("printk: return -EINVAL if
the message len is bigger than the buf size"), and since that commit
widened the possibility for losing a message altogether, the patch
here assumes that this other commit would get reverted first
(otherwise the patch here won't apply).
Furthermore, this patch also addresses the problem dealt with in
commit 4a77a5a06e ("printk: use mutex
lock to stop syslog_seq from going wild"), so I'd recommend reverting
that one too (albeit there's no direct collision between the two).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kay Sievers <kay@vrfy.org>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit b56a39ac26.
A better patch from Jan will follow this to resolve the issue.
Acked-by: Kay Sievers <kay@vrfy.org>
Cc: Fengguang Wu <wfg@linux.intel.com>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 7ff9554bb5 (printk: convert
byte-buffer to variable-length record buffer) introduced a regression
by accidentally removing a "break" statement from inside the big
switch in printk's do_syslog(). The symptom of this bug is that the
"dmesg -C" command doesn't only clear the kernel's log buffer; it also
disables console logging.
This patch (as1561) fixes the regression by adding the missing
"break".
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Just like what devkmsg_read() does, return -EINVAL if the message len is
bigger than the buf size, or it will trigger a segfault error.
Acked-by: Kay Sievers <kay@vrfy.org>
Acked-by: Fengguang Wu <wfg@linux.intel.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Although syslog_seq and log_next_seq stuff are protected by logbuf_lock
spin log, it's not enough. Say we have two processes A and B, and let
syslog_seq = N, while log_next_seq = N + 1, and the two processes both
come to syslog_print at almost the same time. And No matter which
process get the spin lock first, it will increase syslog_seq by one,
then release spin lock; thus later, another process increase syslog_seq
by one again. In this case, syslog_seq is bigger than syslog_next_seq.
And latter, it would make:
wait_event_interruptiable(log_wait, syslog != log_next_seq)
don't wait any more even there is no new write comes. Thus it introduce
a infinite loop reading.
I can easily see this kind of issue by the following steps:
# cat /proc/kmsg # at meantime, I don't kill rsyslog
# So they are the two processes.
# xinit # I added drm.debug=6 in the kernel parameter line,
# so that it will produce lots of message and let that
# issue happen
It's 100% reproducable on my side. And my disk will be filled up by
/var/log/messages in a quite short time.
So, introduce a mutex_lock to stop syslog_seq from going wild just like
what devkmsg_read() does. It does fix this issue as expected.
v2: use mutex_lock_interruptiable() instead (comments from Kay)
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-By: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Provide an iterator to receive the log buffer content, and convert all
kmsg_dump() users to it.
The structured data in the kmsg buffer now contains binary data, which
should no longer be copied verbatim to the kmsg_dump() users.
The iterator should provide reliable access to the buffer data, and also
supports proper log line-aware chunking of data while iterating.
Signed-off-by: Kay Sievers <kay@vrfy.org>
Tested-by: Tony Luck <tony.luck@intel.com>
Reported-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Tested-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 7ff9554bb5, printk: convert
byte-buffer to variable-length record buffer, causes systems using
EABI to crash very early in the boot cycle. The first entry in struct
log is a u64, which for EABI must be 8 byte aligned.
Make use of __alignof__() so the compiler to decide the alignment, but
allow it to be overridden using CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
for systems which can perform unaligned access and want to save
a few bytes of space.
Tested on Orion5x and Kirkwood.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Arrange the continuation printk() buffering to be fully separated from the
ordinary full line users.
Limit the exposure to races and wrong printk() line merges to users of
continuation only. Ordinary full line users racing against continuation
users will no longer affect each other.
Multiple continuation users from different threads, racing against each
other will not wrongly be merged into a single line, but printed as
separate lines.
Test output of a kernel module which starts two separate threads which
race against each other, one of them printing a single full terminated
line:
printk("(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)\n");
The other one printing the line, every character separate in a
continuation loop:
printk("(C");
for (i = 0; i < 58; i++)
printk(KERN_CONT "C");
printk(KERN_CONT "C)\n");
Behavior of single and non-thread-aware printk() buffer:
# modprobe printk-race
printk test init
(CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
(CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
New behavior with separate and thread-aware continuation buffer:
# modprobe printk-race
printk test init
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
(CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
(CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add a stub for prepend_timestamp() when CONFIG_PRINTK is not
enabled. Fixes this build error:
kernel/printk.c:1770:3: error: implicit declaration of function 'prepend_timestamp'
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
__log_buf must be aligned, because a 64-bit value is written directly
to it as part of struct log. Alignment of the log entries is typically
handled by log_store(), but this only triggers for subsequent entries,
not the very first (or wrapped) entries.
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The output of the timestamps got lost with the conversion of the
kmsg buffer to records; restore the old behavior.
Document, that CONFIG_PRINTK_TIME now only controls the output of
the timestamps in the syslog() system call and on the console, and
not the recording of the timestamps.
Cc: Joe Perches <joe@perches.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Reported-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This prevents the merging of printk() continuation lines of different
threads, in the case they race against each other.
It should properly isolate "atomic" single-line printk() users from
continuation users, to make sure the single-line users will never be
merged with the racy continuation ones.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
On Tue, May 8, 2012 at 10:02 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> kernel/built-in.o: In function `devkmsg_read':
> printk.c:(.text+0x27e8): undefined reference to `__udivdi3'
> Most probably the "msg->ts_nsec / 1000" since
> ts_nsec is a u64 and this is a 32 bit build ...
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Support for multiple concurrent readers of /dev/kmsg, with read(),
seek(), poll() support. Output of message sequence numbers, to allow
userspace log consumers to reliably reconnect and reconstruct their
state at any given time. After open("/dev/kmsg"), read() always
returns *all* buffered records. If only future messages should be
read, SEEK_END can be used. In case records get overwritten while
/dev/kmsg is held open, or records get faster overwritten than they
are read, the next read() will return -EPIPE and the current reading
position gets updated to the next available record. The passed
sequence numbers allow the log consumer to calculate the amount of
lost messages.
[root@mop ~]# cat /dev/kmsg
5,0,0;Linux version 3.4.0-rc1+ (kay@mop) (gcc version 4.7.0 20120315 ...
6,159,423091;ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
7,160,424069;pci_root PNP0A03:00: host bridge window [io 0x0000-0x0cf7] (ignored)
SUBSYSTEM=acpi
DEVICE=+acpi:PNP0A03:00
6,339,5140900;NET: Registered protocol family 10
30,340,5690716;udevd[80]: starting version 181
6,341,6081421;FDC 0 is a S82078B
6,345,6154686;microcode: CPU0 sig=0x623, pf=0x0, revision=0x0
7,346,6156968;sr 1:0:0:0: Attached scsi CD-ROM sr0
SUBSYSTEM=scsi
DEVICE=+scsi:1:0:0:0
6,347,6289375;microcode: CPU1 sig=0x623, pf=0x0, revision=0x0
Cc: Karel Zak <kzak@redhat.com>
Tested-by: William Douglas <william.douglas@intel.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
- Record-based stream instead of the traditional byte stream
buffer. All records carry a 64 bit timestamp, the syslog facility
and priority in the record header.
- Records consume almost the same amount, sometimes less memory than
the traditional byte stream buffer (if printk_time is enabled). The record
header is 16 bytes long, plus some padding bytes at the end if needed.
The byte-stream buffer needed 3 chars for the syslog prefix, 15 char for
the timestamp and a newline.
- Buffer management is based on message sequence numbers. When records
need to be discarded, the reading heads move on to the next full
record. Unlike the byte-stream buffer, no old logged lines get
truncated or partly overwritten by new ones. Sequence numbers also
allow consumers of the log stream to get notified if any message in
the stream they are about to read gets discarded during the time
of reading.
- Better buffered IO support for KERN_CONT continuation lines, when printk()
is called multiple times for a single line. The use of KERN_CONT is now
mandatory to use continuation; a few places in the kernel need trivial fixes
here. The buffering could possibly be extended to per-cpu variables to allow
better thread-safety for multiple printk() invocations for a single line.
- Full-featured syslog facility value support. Different facilities
can tag their messages. All userspace-injected messages enforce a
facility value > 0 now, to be able to reliably distinguish them from
the kernel-generated messages. Independent subsystems like a
baseband processor running its own firmware, or a kernel-related
userspace process can use their own unique facility values. Multiple
independent log streams can co-exist that way in the same
buffer. All share the same global sequence number counter to ensure
proper ordering (and interleaving) and to allow the consumers of the
log to reliably correlate the events from different facilities.
Tested-by: William Douglas <william.douglas@intel.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull scheduler changes for v3.4 from Ingo Molnar
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
printk: Make it compile with !CONFIG_PRINTK
sched/x86: Fix overflow in cyc2ns_offset
sched: Fix nohz load accounting -- again!
sched: Update yield() docs
printk/sched: Introduce special printk_sched() for those awkward moments
sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
sched: Cleanup cpu_active madness
sched: Fix load-balance wreckage
sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
sched: Ditch per cgroup task lists for load-balancing
sched: Rename load-balancing fields
sched: Move load-balancing arguments into helper struct
sched/rt: Do not submit new work when PI-blocked
sched/rt: Prevent idle task boosting
sched/wait: Add __wake_up_all_locked() API
sched/rt: Document scheduler related skip-resched-check sites
sched/rt: Use schedule_preempt_disabled()
sched/rt: Add schedule_preempt_disabled()
sched/rt: Do not throttle when PI boosting
sched/rt: Keep period timer ticking when rt throttling is active
...
Commit 3ccf3e8306 ("printk/sched: Introduce special
printk_sched() for those awkward moments") overlooked
an #ifdef, so move code around to respect these directives.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Link: http://lkml.kernel.org/r/1331811337.18960.179.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.
This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since commit 04c6862c05 ("kmsg_dump: add kmsg_dump() calls to the
reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets
run on normal paths including poweroff and reboot.
This is less than ideal given pstore implementations that can only
represent single backtraces, since a reboot may overwrite a stored oops
before it's been picked up by userspace. In addition, some pstore
backends may have low performance and provide a significant delay in
reboot as a result.
This patch adds a printk.always_kmsg_dump kernel parameter (which can also
be changed from userspace). Without it, the code will only be run on
failure paths rather than on normal paths. The option can be enabled in
environments where there's a desire to attempt to audit whether or not a
reboot was cleanly requested or not.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Marco Stornelli <marco.stornelli@gmail.com>
Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a printk.console trace point to record any printk
messages into the trace, regardless of the current
console loglevel. This can help correlate (existing)
printk debugging with other tracing.
Link: http://lkml.kernel.org/r/1322161388.5366.54.camel@jlt3.sipsolutions.net
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
module_param(bool) used to counter-intuitively take an int. In
fddd5201 (mid-2009) we allowed bool or int/unsigned int using a messy
trick.
It's time to remove the int/unsigned int option. For this version
it'll simply give a warning, but it'll break next kernel version.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
You don't need module_param_name if the name is the same!
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Commit 4f2a8d3cf5 ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock. Avoid this.
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Conflicts & resolutions:
* arch/x86/xen/setup.c
dc91c728fd "xen: allow extra memory to be in multiple regions"
24aa07882b "memblock, x86: Replace memblock_x86_reserve/free..."
conflicted on xen_add_extra_mem() updates. The resolution is
trivial as the latter just want to replace
memblock_x86_reserve_range() with memblock_reserve().
* drivers/pci/intel-iommu.c
166e9278a3 "x86/ia64: intel-iommu: move to drivers/iommu/"
5dfe8660a3 "bootmem: Replace work_with_active_regions() with..."
conflicted as the former moved the file under drivers/iommu/.
Resolved by applying the chnages from the latter on the moved
file.
* mm/Kconfig
6661672053 "memblock: add NO_BOOTMEM config symbol"
c378ddd53f "memblock, x86: Make ARCH_DISCARD_MEMBLOCK a config option"
conflicted trivially. Both added config options. Just
letting both add their own options resolves the conflict.
* mm/memblock.c
d1f0ece6cd "mm/memblock.c: small function definition fixes"
ed7b56a799 "memblock: Remove memblock_memory_can_coalesce()"
confliected. The former updates function removed by the
latter. Resolution is trivial.
Signed-off-by: Tejun Heo <tj@kernel.org>
Switch to local_irq_ ops so that the irq state is properly tracked
(raw_local_irq_* isn't tracked by lockdep, causing confusion).
Possible now that commit dd4e5d3ac4 ("lockdep: Fix
trace_[soft,hard]irqs_[on,off]() recursion") cured the reason we
needed the raw_ ops.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The raw_lock_irq_{save,restore}() already implies a
non-preemptibility.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
zap_locks() is used by printk() in a last ditch effort to get data
out, clearly we cannot trust lock state after this so make it disable
lock debugging.
Also don't treat printk recursion through lockdep as a normal
recursion bug but try hard to get the lockdep splat out.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kqxwmo4xz37e1s8w0xopvr0q@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false).
Since the code being updated works because strtoul bombs out (endp isn't
updated) and 0 is returned anyway just remove the check and don't change
the behavior of the function.
Signed-off-by: William Douglas <william.douglas@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false). It should be testing to see if the character less than '0' or
greater than '9' instead. This patch makes that change.
The code being changed worked because strtoul bombs out (endp isn't
updated) and 0 is returned anyway.
Signed-off-by: William Douglas <william.douglas@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We are enabling some power features on medfield. To test suspend-2-RAM
conveniently, we need turn on/off console_suspend_enabled frequently.
Add a module parameter, so users could change it by:
/sys/module/printk/parameters/console_suspend
Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We are enabling some power features on medfield. To test suspend-2-RAM
conveniently, we need turn on/off ignore_loglevel frequently without
rebooting.
Add a module parameter, so users can change it by:
/sys/module/printk/parameters/ignore_loglevel
Signed-off-by: Yanmin Zhang <yanmin.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The logbuf_lock lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.
In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ merged and fixed it ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It seems that 7bf693951a ("console: allow to retain boot console via
boot option keep_bootcon") doesn't always achieve what it aims, as when
printk_late_init() runs it unconditionally turns off all boot consoles.
With this patch, I am able to see more messages on the boot console in
KVM guests than I can without, when keep_bootcon is specified.
I think it is appropriate for the relevant -stable trees. However, it's
more of an annoyance than a serious bug (ideally you don't need to keep
the boot console around as console handover should be working -- I was
encountering a situation where the console handover wasn't working and
not having the boot console available meant I couldn't see why).
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg KH <gregkh@suse.de>
Acked-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Cc: <stable@kernel.org> [2.6.39.x, 3.0.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
syslog-ng versions before 3.3.0beta1 (2011-05-12) assume that
CAP_SYS_ADMIN is sufficient to access syslog, so ever since CAP_SYSLOG
was introduced (2010-11-25) they have triggered a warning.
Commit ee24aebffb ("cap_syslog: accept CAP_SYS_ADMIN for now")
improved matters a little by making syslog-ng work again, just keeping
the WARN_ONCE(). But still, this is a warning that writes a stack trace
we don't care about to syslog, sets a taint flag, and alarms sysadmins
when nothing worse has happened than use of an old userspace with a
recent kernel.
Convert the WARN_ONCE to a printk_once to avoid that while continuing to
give userspace developers a hint that this is an unwanted
backward-compatibility feature and won't be around forever.
Reported-by: Ralf Hildebrandt <ralf.hildebrandt@charite.de>
Reported-by: Niels <zorglub_olsen@hotmail.com>
Reported-by: Paweł Sikora <pluto@agmk.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Liked-by: Gergely Nagy <algernon@madhouse-project.org>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kay Sievers