The "reason" can come from skb->data[] and it hasn't been capped so it
can be from 0-255 instead of just 0-6. For example in irlmp_state_dtr()
the code does:
reason = skb->data[3];
...
irlmp_disconnect_indication(self, reason, skb);
Also LMREASON has a couple other values which don't have entries in the
irlmp_reasons[] array. And 0xff is a valid reason as well which means
"unknown".
So far as I can see we don't actually care about "reason" except for in
the debug code.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
As reported by Dave Kleikamp, when we emit cross calls to do batched
TLB flush processing we have a race because we do not synchronize on
the sibling cpus completing the cross call.
So meanwhile the TLB batch can be reset (tb->tlb_nr set to zero, etc.)
and either flushes are missed or flushes will flush the wrong
addresses.
Fix this by using generic infrastructure to synchonize on the
completion of the cross call.
This first required getting the flush_tlb_pending() call out from
switch_to() which operates with locks held and interrupts disabled.
The problem is that smp_call_function_many() cannot be invoked with
IRQs disabled and this is explicitly checked for with WARN_ON_ONCE().
We get the batch processing outside of locked IRQ disabled sections by
using some ideas from the powerpc port. Namely, we only batch inside
of arch_{enter,leave}_lazy_mmu_mode() calls. If we're not in such a
region, we flush TLBs synchronously.
1) Get rid of xcall_flush_tlb_pending and per-cpu type
implementations.
2) Do TLB batch cross calls instead via:
smp_call_function_many()
tlb_pending_func()
__flush_tlb_pending()
3) Batch only in lazy mmu sequences:
a) Add 'active' member to struct tlb_batch
b) Define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
c) Set 'active' in arch_enter_lazy_mmu_mode()
d) Run batch and clear 'active' in arch_leave_lazy_mmu_mode()
e) Check 'active' in tlb_batch_add_one() and do a synchronous
flush if it's clear.
4) Add infrastructure for synchronous TLB page flushes.
a) Implement __flush_tlb_page and per-cpu variants, patch
as needed.
b) Likewise for xcall_flush_tlb_page.
c) Implement smp_flush_tlb_page() to invoke the cross-call.
d) Wire up global_flush_tlb_page() to the right routine based
upon CONFIG_SMP
5) It turns out that singleton batches are very common, 2 out of every
3 batch flushes have only a single entry in them.
The batch flush waiting is very expensive, both because of the poll
on sibling cpu completeion, as well as because passing the tlb batch
pointer to the sibling cpus invokes a shared memory dereference.
Therefore, in flush_tlb_pending(), if there is only one entry in
the batch perform a completely asynchronous global_flush_tlb_page()
instead.
Reported-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>
cyc_to_sched_clock() is called by sched_clock() and cyc_to_ns()
is called by cyc_to_sched_clock(). I suspect that some compilers
inline both of these functions into sched_clock() and so we've
been getting away without having a notrace marking. It seems that
my compiler isn't inlining cyc_to_sched_clock() though, so I'm
hitting a recursion bug when I enable the function graph tracer,
causing my system to crash. Marking these functions notrace fixes
it. Technically cyc_to_ns() doesn't need the notrace because it's
already marked inline, but let's just add it so that if we ever
remove inline from that function it doesn't blow up.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This enum leaks out to userspace via error messages, so fix the spelling.
Signed-off-by: Bill Nottingham <notting@redhat.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
While writting to device is limitted to max_msg_length advertized
in client properites the read can be much longer delivered consequiting chunks.
We use krealloc to enlarge the buffer when needed.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1. Rename the function and change parameters order,
so that first parameter is mei_device
2. Simplify the function code flow
3. Rename helper functions to more self descriptive names
4. Use helpers common functions where possible
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that Joe cleaned up the init/exit functions, we can just get rid of
them entirely and use the proper macro that almost all other USB drivers
now use.
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use a more current logging style with dev_printk
where possible.
o Convert uses of US_DEBUGP to usb_stor_dbg
o Add "struct us_data *" to usb_stor_dbg uses
o usb_stor_dbg now uses struct device */dev_vprint_emit
o Removed embedded function names
o Coalesce formats
o Remove trailing whitespace
o Remove useless OOM messages
o Remove useless function entry/exit logging
o Convert some US_DEBUGP uses to dev_info and dev_dbg
Object size is slightly reduced when debugging
is enabled, slightly increased with no debugging
because some initialization and removal messages
are now always emitted.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Only one remaining fix for arm-soc platforms at this time, a small
bugfix for cpu hotplug on highbank platforms that has become much
easier to hit as of late. Details in the patch description, but it's
small and well-contained and definitely impacts users of the platform,
so 3.9 seems appropriate.
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Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
Pull ARM SoC fixes from Olof Johansson:
"Only one remaining fix for arm-soc platforms at this time, a small
bugfix for cpu hotplug on highbank platforms that has become much
easier to hit as of late.
Details in the patch description, but it's small and well-contained
and definitely impacts users of the platform, so 3.9 seems
appropriate."
* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
ARM: highbank: fix cache flush ordering for cpu hotplug
Pablo Neira Ayuso says:
====================
If time allows, please consider pulling the following patchset contains two
late Netfilter fixes, they are:
* Skip broadcast/multicast locally generated traffic in the rpfilter,
(closes netfilter bugzilla #814), from Florian Westphal.
* Fix missing elements in the listing of ipset bitmap ip,mac set
type with timeout support enabled, from Jozsef Kadlecsik.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
John W. Linville says:
====================
A few stragglers hoping for 3.9, somewhat delayed due to my travels...
On the mac80211 bits, Johannes says:
"Sadly, I have another pull request -- the idle handling fix broke LED
handling in some cases."
and:
"Yet one more!
This fixes a fairly important/annoying bug -- when roaming between
multiple APs of the same network, the system could get stuck thinking it
was connected to the old one while it really wasn't."
On top of that...
Arend sends a brcmfmac patch that removes advertising a feature that
isn't actually fully supported, and a brcmsmac patch that rearranges
code to request firmware at IFF_UP to play more nicely with being
built into the kernel.
Felix gives us a minor ath9k_htc fix to support the newly released
open source firmware, and an ath9k_hw initvals fix to improve device
stability.
Rafał Miłecki provides a fix for an ssb regression that caused a
serious performance problem with b43.
Zefir Kurtisi offers an ath9k fix to change some kmalloc flags to
allow the DFS detector to be called in softirq context.
Please let me know if there are problems. If these don't make 3.9,
I'll just pull them into wireless-next -- just let me know if you
want to do it that way!
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Rename the function to mei_amthif_irq_read_msg
and change parameters order
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit bd090dfc63 (tcp: tcp_replace_ts_recent() should not be called
from tcp_validate_incoming()) introduced a TS ecr bug in slow path
processing.
1 A > B P. 1:10001(10000) ack 1 <nop,nop,TS val 1001 ecr 200>
2 B < A . 1:1(0) ack 1 win 257 <sack 9001:10001,TS val 300 ecr 1001>
3 A > B . 1:1001(1000) ack 1 win 227 <nop,nop,TS val 1002 ecr 200>
4 A > B . 1001:2001(1000) ack 1 win 227 <nop,nop,TS val 1002 ecr 200>
(ecr 200 should be ecr 300 in packets 3 & 4)
Problem is tcp_ack() can trigger send of new packets (retransmits),
reflecting the prior TSval, instead of the TSval contained in the
currently processed incoming packet.
Fix this by calling tcp_replace_ts_recent() from tcp_ack() after the
checks, but before the actions.
Reported-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
All the legacy comedi drivers now call comedi_legacy_detach()
either directly or as part of their (*detach). Move the free_irq()
into comedi_legacy_detach() so that the drivers don't have to
deal with it.
For drivers that then only call comedi_legacy_detach() in their
private (*detach), remove the private function and use the helper
directly for the (*detach).
The amplc_pc236 and ni_labpc drivers are hybrid legacy/PCI drivers.
In the detach of a PCI board free_irq() still needs to be handled
by the driver.
The pcl724 and pcl726 drivers currently have the free_irq() #ifdef'ed
out. The comedi_legacy_detach() function sanity checks that the irq
has been requested before freeing it so they are safe to convert.
For aesthetic reasons, move the #ifdef unused chunk in the pcl816
driver up to the previous #ifdef unused block.
The pcmio and pcmuio drivers request multiple irqs and handle the
freeing of them. Remove the 'dev->irq = irq[0]' in those drivers
so that comedi_legacy_detach() does not attempt to free the irq.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use comedi_legacy_detach() to release the I/O region requested
by these drivers.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Update the skeleton driver to use the new comedi_legacy_detach()
helper in the (*detach) to release the I/O region. Also, update
the comment about it.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The I/O region used by this driver is always requested using
comedi_request_region(). The devpriv->io union is only used by
the common code shared by the legacy and PCI drivers.
Use the new comedi_legacy_detach() helper in the (*detach) to
release the I/O region requested by this driver. That function
will handle the proper sanity checking before releasing the
resource.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use the new comedi_legacy_detach() helper in the (*detach) to release
the I/O region requested by these drivers.
Since the (*detach) for these drivers only releases the region, remove
the private (*detach) functions and use comedi_legacy_detach() directly
for the (*detach).
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use the new comedi_legacy_detach() helper in the (*detach) to release
the first I/O region requested by this driver.
An additional I/O region is requested for some of the boards this driver
supports. The iobase for that region is stored in the private data so
that the (*detach) knows it needs to be released. Remove the extra
cleanup in the (*attach) that releases the first region.
For aesthetics, move the release of the additional region in the
(*detach) so it follows the (*attach) order.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Make sure to check if subdev_8255_init() fails and propogate the
error code.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use the new comedi_legacy_detach() helper in the (*detach) to release
the first I/O region requested by this driver.
An additional I/O region is requested by this driver for the 8255
device. Save the iobase for that region in the private data so that
the (*detach) knows it needs to be released.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use the new comedi_legacy_detach() helper in the (*detach) to release
the first I/O region requested by this driver.
An additional I/O region is requested for some of the boards this driver
supports. Save the iobase for that region in the private data so that
the (*detach) knows it needs to be released.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This driver does not follow the standard (*attach) (*detach) flow of
the other drivers in comedi. Comedi drivers do not 'cleanup' any of
the allocations made during the (*attach) if failures are encountered.
If the (*attach) fails, the comedi core will call the (*detach) to
handle any clenaup.
In this driver, the function free_resources() handles all the cleanup.
Remove the calls to this function during the (*attach). Since the
(*detach) is then the only caller, remove the function and just put
all the cleanup in the (*detach) function.
Use the new comedi_legacy_detach() helper in the (*detach) to release
the I/O region.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This function is intended to be used by the comedi legacy (ISA) drivers
either directly as the (*detach) function or as a helper in the drivers
private (*detach) function.
Modify the comedi_request_region() helper so that it stores the 'len' of
the region as well as the 'start' after the region has been successfuly
allocated by request_region() in __comedi_request_region(). This region
will then be automatically released detach of the driver by the
comedi_legacy_detach() helper.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The custom filename function mostly repeats the kernel's kbasename. This patch
simplifies it. The updated filename() will not check for the '\' in the
filenames. It seems redundant in Linux. The __FILE__ macro always defined if we
compile an existing file. Thus, NULL check is not needed there as well.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To quote the TODO from staging/net/:
PC300:
The driver is very broken and cannot work with the current TTY
layer. It is inevitable to convert it to the new TTY API. If no
one steps in to adopt the driver, it will be removed in the 3.7
release.
Nothing has changed since more than _one_ year on this driver, thus
just remove it since we already moved past 3.7. If somebody steps
up and does a whole rework, he/she, of course, is free to resubmit
it. Since this is the only one in the net directory, we can remove
it as well.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1. Rename init_clients_state to hbm_state and use
MEI_HBM_ prefix for HBM states
2. Remove recvd_msg and use hbm state for synchronizing
hbm protocol has successful start.
We can wake up the hbm event from start response handler
and remove the hack from the interrupt thread
3. mei_hbm_start_wait function encapsulate start completion
waiting
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Kill custom closing_wait implementation and let the tty-layer handle it
instead.
Note that the port drain-delay is set to three characters to keep the
20ms delay after wait_until_sent at low baudrates (1200 baud) during close.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Remove redundant drain, which has already been handled by the tty-layer,
from break_ctl.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Query hardware-buffer status in chars_in_buffer should the write fifo be
empty.
This is needed to make the tty layer wait for hardware buffers to drain
on close.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The line status register is only polled so let's not keep a possibly
outdated value in the port data.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move write-fifo flushing from ti_drain to close where it belongs.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Remove redundant wait_until_sent, which has already been handled by the
tty-layer, from break_ctl.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fix regression introduced by commit f40d78155 ("USB: io_ti: kill custom
closing_wait implementation") which made TIOCGSERIAL return the wrong
value for closing_wait.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Cc: stable <stable@vger.kernel.org> # 3.9
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Inside usbtmc_ioctl_clear_out_halt()/usbtmc_ioctl_clear_in_halt(),
usb_clear_halt() needn't any buffer to pass in, so remove the
unnecessary memory allocation.
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The dereference to 'instance' in the debug code should be moved
below the NULL test.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This is my example conversion of a few existing mmap users. The pcm
mmap case is one of the more straightforward ones.
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is my example conversion of a few existing mmap users. The
fb_mmap() case is a good example because it is a bit more complicated
than some: fb_mmap() mmaps one of two different memory areas depending
on the page offset of the mmap (but happily there is never any mixing of
the two, so the helper function still works).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is my example conversion of a few existing mmap users. The mtdchar
case is actually disabled right now (and stays disabled), but I did it
because it showed up on my "git grep", and I was familiar with the code
due to fixing an overflow problem in the code in commit 9c603e53d3
("mtdchar: fix offset overflow detection").
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is my example conversion of a few existing mmap users. The HPET
case is simple, widely available, and easy to test (Clemens Ladisch sent
a trivial test-program for it).
Test-program-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull input fixes from Dmitry Torokhov:
"Two more small fixups to the wacom driver"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
Input: wacom - fix "can not retrieve extra class descriptor" for DTH2242
Input: wacom - DTH2242 Grip Pen id was off by one bit
Pull fuse build fix from Miklos Szeredi:
"This fixes android builds. The patch appears large, but is just
search & replace."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: fix type definitions in uapi header
Same as Cintiq 24HDT, DTH2242 has two interfaces sharing one configuration.
This patch ignores the second interface.
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
The following resolves a section mismatch warning below in xen-acpi-processor introduced by
3fac10145b [13/13] xen: Re-upload processor PM data to hypervisor after S3 resume (v2)
Warning:
WARNING: drivers/xen/built-in.o(.text+0x2056a): Section mismatch in reference from the function xen_upload_processor_pm_data() to the function .init.text:read_acpi_id()
The function xen_upload_processor_pm_data() references
the function __init read_acpi_id().
This is often because xen_upload_processor_pm_data lacks a __init
annotation or the annotation of read_acpi_id is wrong.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Ben Guthro <benjamin.guthro@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This update adds a debugfs interface to modify a pin configuration
for a given state in the pinctrl map. This allows to modify the
configuration for a non-active state, typically sleep state.
This configuration is not applied right away, but only when the state
will be entered.
This solution is mandated for us by HW validation: in order
to test and verify several pin configurations during sleep without
recompiling the software.
Change log in this patch set;
Take into account latest feedback from Stephen Warren:
- stale comments update
- improved code efficiency and readibility
- limit size of global variable pinconf_dbg_conf
- remove req_type as it can easily be added later when
add/delete requests support is implemented
Signed-off-by: Laurent Meunier <laurent.meunier@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Linus suggested that probably all the supported architectures can
allow a negative mutex count without incorrect behavior, so we can
then back out the architecture specific change and allow the
mutex count to go to any negative number. That should further
reduce contention for non-x86 architecture.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Norton Scott J <scott.norton@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-5-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The current mutex spinning code (with MUTEX_SPIN_ON_OWNER option
turned on) allow multiple tasks to spin on a single mutex
concurrently. A potential problem with the current approach is
that when the mutex becomes available, all the spinning tasks
will try to acquire the mutex more or less simultaneously. As a
result, there will be a lot of cacheline bouncing especially on
systems with a large number of CPUs.
This patch tries to reduce this kind of contention by putting
the mutex spinners into a queue so that only the first one in
the queue will try to acquire the mutex. This will reduce
contention and allow all the tasks to move forward faster.
The queuing of mutex spinners is done using an MCS lock based
implementation which will further reduce contention on the mutex
cacheline than a similar ticket spinlock based implementation.
This patch will add a new field into the mutex data structure
for holding the MCS lock. This expands the mutex size by 8 bytes
for 64-bit system and 4 bytes for 32-bit system. This overhead
will be avoid if the MUTEX_SPIN_ON_OWNER option is turned off.
The following table shows the jobs per minute (JPM) scalability
data on an 8-node 80-core Westmere box with a 3.7.10 kernel. The
numactl command is used to restrict the running of the fserver
workloads to 1/2/4/8 nodes with hyperthreading off.
+-----------------+-----------+-----------+-------------+----------+
| Configuration | Mean JPM | Mean JPM | Mean JPM | % Change |
| | w/o patch | patch 1 | patches 1&2 | 1->1&2 |
+-----------------+------------------------------------------------+
| | User Range 1100 - 2000 |
+-----------------+------------------------------------------------+
| 8 nodes, HT off | 227972 | 227237 | 305043 | +34.2% |
| 4 nodes, HT off | 393503 | 381558 | 394650 | +3.4% |
| 2 nodes, HT off | 334957 | 325240 | 338853 | +4.2% |
| 1 node , HT off | 198141 | 197972 | 198075 | +0.1% |
+-----------------+------------------------------------------------+
| | User Range 200 - 1000 |
+-----------------+------------------------------------------------+
| 8 nodes, HT off | 282325 | 312870 | 332185 | +6.2% |
| 4 nodes, HT off | 390698 | 378279 | 393419 | +4.0% |
| 2 nodes, HT off | 336986 | 326543 | 340260 | +4.2% |
| 1 node , HT off | 197588 | 197622 | 197582 | 0.0% |
+-----------------+-----------+-----------+-------------+----------+
At low user range 10-100, the JPM differences were within +/-1%.
So they are not that interesting.
The fserver workload uses mutex spinning extensively. With just
the mutex change in the first patch, there is no noticeable
change in performance. Rather, there is a slight drop in
performance. This mutex spinning patch more than recovers the
lost performance and show a significant increase of +30% at high
user load with the full 8 nodes. Similar improvements were also
seen in a 3.8 kernel.
The table below shows the %time spent by different kernel
functions as reported by perf when running the fserver workload
at 1500 users with all 8 nodes.
+-----------------------+-----------+---------+-------------+
| Function | % time | % time | % time |
| | w/o patch | patch 1 | patches 1&2 |
+-----------------------+-----------+---------+-------------+
| __read_lock_failed | 34.96% | 34.91% | 29.14% |
| __write_lock_failed | 10.14% | 10.68% | 7.51% |
| mutex_spin_on_owner | 3.62% | 3.42% | 2.33% |
| mspin_lock | N/A | N/A | 9.90% |
| __mutex_lock_slowpath | 1.46% | 0.81% | 0.14% |
| _raw_spin_lock | 2.25% | 2.50% | 1.10% |
+-----------------------+-----------+---------+-------------+
The fserver workload for an 8-node system is dominated by the
contention in the read/write lock. Mutex contention also plays a
role. With the first patch only, mutex contention is down (as
shown by the __mutex_lock_slowpath figure) which help a little
bit. We saw only a few percents improvement with that.
By applying patch 2 as well, the single mutex_spin_on_owner
figure is now split out into an additional mspin_lock figure.
The time increases from 3.42% to 11.23%. It shows a great
reduction in contention among the spinners leading to a 30%
improvement. The time ratio 9.9/2.33=4.3 indicates that there
are on average 4+ spinners waiting in the spin_lock loop for
each spinner in the mutex_spin_on_owner loop. Contention in
other locking functions also go down by quite a lot.
The table below shows the performance change of both patches 1 &
2 over patch 1 alone in other AIM7 workloads (at 8 nodes,
hyperthreading off).
+--------------+---------------+----------------+-----------------+
| Workload | mean % change | mean % change | mean % change |
| | 10-100 users | 200-1000 users | 1100-2000 users |
+--------------+---------------+----------------+-----------------+
| alltests | 0.0% | -0.8% | +0.6% |
| five_sec | -0.3% | +0.8% | +0.8% |
| high_systime | +0.4% | +2.4% | +2.1% |
| new_fserver | +0.1% | +14.1% | +34.2% |
| shared | -0.5% | -0.3% | -0.4% |
| short | -1.7% | -9.8% | -8.3% |
+--------------+---------------+----------------+-----------------+
The short workload is the only one that shows a decline in
performance probably due to the spinner locking and queuing
overhead.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Norton Scott J <scott.norton@hp.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-4-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In the __mutex_lock_common() function, an initial entry into
the lock slow path will cause two atomic_xchg instructions to be
issued. Together with the atomic decrement in the fast path, a
total of three atomic read-modify-write instructions will be
issued in rapid succession. This can cause a lot of cache
bouncing when many tasks are trying to acquire the mutex at the
same time.
This patch will reduce the number of atomic_xchg instructions
used by checking the counter value first before issuing the
instruction. The atomic_read() function is just a simple memory
read. The atomic_xchg() function, on the other hand, can be up
to 2 order of magnitude or even more in cost when compared with
atomic_read(). By using atomic_read() to check the value first
before calling atomic_xchg(), we can avoid a lot of unnecessary
cache coherency traffic. The only downside with this change is
that a task on the slow path will have a tiny bit less chance of
getting the mutex when competing with another task in the fast
path.
The same is true for the atomic_cmpxchg() function in the
mutex-spin-on-owner loop. So an atomic_read() is also performed
before calling atomic_cmpxchg().
The mutex locking and unlocking code for the x86 architecture
can allow any negative number to be used in the mutex count to
indicate that some tasks are waiting for the mutex. I am not so
sure if that is the case for the other architectures. So the
default is to avoid atomic_xchg() if the count has already been
set to -1. For x86, the check is modified to include all
negative numbers to cover a larger case.
The following table shows the jobs per minutes (JPM) scalability
data on an 8-node 80-core Westmere box with a 3.7.10 kernel. The
numactl command is used to restrict the running of the
high_systime workloads to 1/2/4/8 nodes with hyperthreading on
and off.
+-----------------+-----------+------------+----------+
| Configuration | Mean JPM | Mean JPM | % Change |
| | w/o patch | with patch | |
+-----------------+-----------------------------------+
| | User Range 1100 - 2000 |
+-----------------+-----------------------------------+
| 8 nodes, HT on | 36980 | 148590 | +301.8% |
| 8 nodes, HT off | 42799 | 145011 | +238.8% |
| 4 nodes, HT on | 61318 | 118445 | +51.1% |
| 4 nodes, HT off | 158481 | 158592 | +0.1% |
| 2 nodes, HT on | 180602 | 173967 | -3.7% |
| 2 nodes, HT off | 198409 | 198073 | -0.2% |
| 1 node , HT on | 149042 | 147671 | -0.9% |
| 1 node , HT off | 126036 | 126533 | +0.4% |
+-----------------+-----------------------------------+
| | User Range 200 - 1000 |
+-----------------+-----------------------------------+
| 8 nodes, HT on | 41525 | 122349 | +194.6% |
| 8 nodes, HT off | 49866 | 124032 | +148.7% |
| 4 nodes, HT on | 66409 | 106984 | +61.1% |
| 4 nodes, HT off | 119880 | 130508 | +8.9% |
| 2 nodes, HT on | 138003 | 133948 | -2.9% |
| 2 nodes, HT off | 132792 | 131997 | -0.6% |
| 1 node , HT on | 116593 | 115859 | -0.6% |
| 1 node , HT off | 104499 | 104597 | +0.1% |
+-----------------+------------+-----------+----------+
At low user range 10-100, the JPM differences were within +/-1%.
So they are not that interesting.
AIM7 benchmark run has a pretty large run-to-run variance due to
random nature of the subtests executed. So a difference of less
than +-5% may not be really significant.
This patch improves high_systime workload performance at 4 nodes
and up by maintaining transaction rates without significant
drop-off at high node count. The patch has practically no
impact on 1 and 2 nodes system.
The table below shows the percentage time (as reported by perf
record -a -s -g) spent on the __mutex_lock_slowpath() function
by the high_systime workload at 1500 users for 2/4/8-node
configurations with hyperthreading off.
+---------------+-----------------+------------------+---------+
| Configuration | %Time w/o patch | %Time with patch | %Change |
+---------------+-----------------+------------------+---------+
| 8 nodes | 65.34% | 0.69% | -99% |
| 4 nodes | 8.70% | 1.02% | -88% |
| 2 nodes | 0.41% | 0.32% | -22% |
+---------------+-----------------+------------------+---------+
It is obvious that the dramatic performance improvement at 8
nodes was due to the drastic cut in the time spent within the
__mutex_lock_slowpath() function.
The table below show the improvements in other AIM7 workloads
(at 8 nodes, hyperthreading off).
+--------------+---------------+----------------+-----------------+
| Workload | mean % change | mean % change | mean % change |
| | 10-100 users | 200-1000 users | 1100-2000 users |
+--------------+---------------+----------------+-----------------+
| alltests | +0.6% | +104.2% | +185.9% |
| five_sec | +1.9% | +0.9% | +0.9% |
| fserver | +1.4% | -7.7% | +5.1% |
| new_fserver | -0.5% | +3.2% | +3.1% |
| shared | +13.1% | +146.1% | +181.5% |
| short | +7.4% | +5.0% | +4.2% |
+--------------+---------------+----------------+-----------------+
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Norton: Scott J <scott.norton@hp.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-3-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Dan Carpenter