linux-stable.git/kernel, branch linux-2.6.39.y

taskstats: don't allow duplicate entries in listener mode

2011-07-09T06:15:34+00:00

commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream.

Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process
terminations.

Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003.  It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.

The patch limits the number of times a single process may register
itself on a single CPU to one.

One little issue is kept unfixed - as taskstats_exit() is called before
exit_files() in do_exit(), the orphaned listener entry (if it was not
explicitly deregistered) is kept until the next someone's exit() and
implicit deregistration in send_cpu_listeners().  So, if a process
registered itself as a listener exits and the next spawned process gets
the same pid, it would inherit taskstats attributes.

Signed-off-by: Vasiliy Kulikov 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

PM / Hibernate: Fix free_unnecessary_pages()

2011-07-09T06:15:27+00:00

commit 4d4cf23cdde2f8f9324f5684a7f349e182039529 upstream.

There is a bug in free_unnecessary_pages() that causes it to
attempt to free too many pages in some cases, which triggers the
BUG_ON() in memory_bm_clear_bit() for copy_bm.  Namely, if
count_data_pages() is initially greater than alloc_normal, we get
to_free_normal equal to 0 and "save" greater from 0.  In that case,
if the sum of "save" and count_highmem_pages() is greater than
alloc_highmem, we subtract a positive number from to_free_normal.
Hence, since to_free_normal was 0 before the subtraction and is
an unsigned int, the result is converted to a huge positive number
that is used as the number of pages to free.

Fix this bug by checking if to_free_normal is actually greater
than or equal to the number we're going to subtract from it.

Signed-off-by: Rafael J. Wysocki 
Reported-and-tested-by: Matthew Garrett 
Signed-off-by: Greg Kroah-Hartman

PM: Free memory bitmaps if opening /dev/snapshot fails

2011-07-09T06:15:09+00:00

commit 8440f4b19494467883f8541b7aa28c7bbf6ac92b upstream.

When opening /dev/snapshot device, snapshot_open() creates memory
bitmaps which are freed in snapshot_release(). But if any of the
callbacks called by pm_notifier_call_chain() returns NOTIFY_BAD, open()
fails, snapshot_release() is never called and bitmaps are not freed.
Next attempt to open /dev/snapshot then triggers BUG_ON() check in
create_basic_memory_bitmaps(). This happens e.g. when vmwatchdog module
is active on s390x.

Signed-off-by: Michal Kubecek 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

clocksource: Make watchdog robust vs. interruption

2011-07-09T06:15:05+00:00

commit b5199515c25cca622495eb9c6a8a1d275e775088 upstream.

The clocksource watchdog code is interruptible and it has been
observed that this can trigger false positives which disable the TSC.

The reason is that an interrupt storm or a long running interrupt
handler between the read of the watchdog source and the read of the
TSC brings the two far enough apart that the delta is larger than the
unstable treshold. Move both reads into a short interrupt disabled
region to avoid that.

Reported-and-tested-by: Vernon Mauery 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

genirq: Fix descriptor init on non-sparse IRQs

2011-06-23T22:05:35+00:00

commit e7fbad300a7a6432238f086e3c9a61538a905858 upstream.

The genirq changes are initializing descriptors for sparse IRQs quite
differently from how non-sparse (stacked?) IRQs are initialized, with
the effect that on my platform all IRQs are default-disabled on sparse
IRQs and default-enabled if non-sparse IRQs are used, crashing some
GPIO driver.

Fix this by refactoring the non-sparse IRQs to use the same descriptor
init function as the sparse IRQs.

Signed-off: Linus Walleij 
Link: http://lkml.kernel.org/r/1306858479-16622-1-git-send-email-linus.walleij@stericsson.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

lockdep: Fix lock_is_held() on recursion

2011-06-23T22:05:35+00:00

commit f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d upstream.

The main lock_is_held() user is lockdep_assert_held(), avoid false
assertions in lockdep_off() sections by unconditionally reporting the
lock is taken.

[ the reason this is important is a lockdep_assert_held() in ttwu()
  which triggers a warning under lockdep_off() as in printk() which
  can trigger another wakeup and lock up due to spinlock
  recursion, as reported and heroically debugged by Arne Jansen ]

Reported-and-tested-by: Arne Jansen 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

idle governor: Avoid lock acquisition to read pm_qos before entering idle

2011-06-03T00:32:35+00:00

commit 333c5ae9948194428fe6c5ef5c088304fc98263b upstream.

Thanks to the reviews and comments by Rafael, James, Mark and Andi.
Here's version 2 of the patch incorporating your comments and also some
update to my previous patch comments.

I noticed that before entering idle state, the menu idle governor will
look up the current pm_qos target value according to the list of qos
requests received.  This look up currently needs the acquisition of a
lock to access the list of qos requests to find the qos target value,
slowing down the entrance into idle state due to contention by multiple
cpus to access this list.  The contention is severe when there are a lot
of cpus waking and going into idle.  For example, for a simple workload
that has 32 pair of processes ping ponging messages to each other, where
64 cpu cores are active in test system, I see the following profile with
37.82% of cpu cycles spent in contention of pm_qos_lock:

-     37.82%          swapper  [kernel.kallsyms]          [k]
_raw_spin_lock_irqsave
   - _raw_spin_lock_irqsave
      - 95.65% pm_qos_request
           menu_select
           cpuidle_idle_call
         - cpu_idle
              99.98% start_secondary

A better approach will be to cache the updated pm_qos target value so
reading it does not require lock acquisition as in the patch below.
With this patch the contention for pm_qos_lock is removed and I saw a
2.2X increase in throughput for my message passing workload.

Signed-off-by: Tim Chen 
Acked-by: Andi Kleen 
Acked-by: James Bottomley 
Acked-by: mark gross 
Signed-off-by: Len Brown 
Signed-off-by: Greg Kroah-Hartman

ftrace: Only update the function code on write to filter files

2011-06-03T00:31:27+00:00

commit 058e297d34a404caaa5ed277de15698d8dc43000 upstream.

If function tracing is enabled, a read of the filter files will
cause the call to stop_machine to update the function trace sites.
It should only call stop_machine on write.

Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-05-17T15:02:04+00:00

* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  tick: Clear broadcast active bit when switching to oneshot
  rtc: mc13xxx: Don't call rtc_device_register while holding lock
  rtc: rp5c01: Initialize drvdata before registering device
  rtc: pcap: Initialize drvdata before registering device
  rtc: msm6242: Initialize drvdata before registering device
  rtc: max8998: Initialize drvdata before registering device
  rtc: max8925: Initialize drvdata before registering device
  rtc: m41t80: Initialize clientdata before registering device
  rtc: ds1286: Initialize drvdata before registering device
  rtc: ep93xx: Initialize drvdata before registering device
  rtc: davinci: Initialize drvdata before registering device
  rtc: mxc: Initialize drvdata before registering device
  clocksource: Install completely before selecting

tick: Clear broadcast active bit when switching to oneshot

2011-05-16T21:35:41+00:00

The first cpu which switches from periodic to oneshot mode switches
also the broadcast device into oneshot mode. The broadcast device
serves as a backup for per cpu timers which stop in deeper
C-states. To avoid starvation of the cpus which might be in idle and
depend on broadcast mode it marks the other cpus as broadcast active
and sets the brodcast expiry value of those cpus to the next tick.

The oneshot mode broadcast bit for the other cpus is sticky and gets
only cleared when those cpus exit idle. If a cpu was not idle while
the bit got set in consequence the bit prevents that the broadcast
device is armed on behalf of that cpu when it enters idle for the
first time after it switched to oneshot mode.

In most cases that goes unnoticed as one of the other cpus has usually
a timer pending which keeps the broadcast device armed with a short
timeout. Now if the only cpu which has a short timer active has the
bit set then the broadcast device will not be armed on behalf of that
cpu and will fire way after the expected timer expiry. In the case of
Christians bug report it took ~145 seconds which is about half of the
wrap around time of HPET (the limit for that device) due to the fact
that all other cpus had no timers armed which expired before the 145
seconds timeframe.

The solution is simply to clear the broadcast active bit
unconditionally when a cpu switches to oneshot mode after the first
cpu switched the broadcast device over. It's not idle at that point
otherwise it would not be executing that code.

[ I fundamentally hate that broadcast crap. Why the heck thought some
  folks that when going into deep idle it's a brilliant concept to
  switch off the last device which brings the cpu back from that
  state? ]

Thanks to Christian for providing all the valuable debug information!

Reported-and-tested-by: Christian Hoffmann 
Cc: John Stultz 
Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1105161105170.3078%40ionos%3E
Cc: stable@kernel.org
Signed-off-by: Thomas Gleixner