Commit Graph

13607 Commits

Author SHA1 Message Date
Linus Torvalds
9a2bc8603e Merge branch 'anton-kgdb' (kgdb dmesg fixups)
Merge emailed kgdb dmesg fixups patches from Anton Vorontsov:
 "The dmesg command appears to be broken after the printk rework.  The
  old logic in the kdb code makes no sense in terms of current
  printk/logging storage format, and KDB simply hangs forever upon
  entering 'dmesg' command.

  The first patch revives the command by switching to kmsg_dumper
  iterator.  As a side-effect, the code is now much more simpler.

  A few changes were needed in the printk.c: we needed unlocked variant
  of the kmsg_dumper iterator, but these can surely wait for 3.6.

  It's probably too late even for the first patch to go to 3.5, but I'll
  try to convince otherwise.  :-) Here we go:

   - The current code is broken for sure, and has no hope to work at
     all.  It is a regression
   - The new code works for me, and probably works for everyone else;
   - If it compiles (and I urge everyone to compile-test it on your
     setup), it hardly can make things worse."

* Merge emailed patches from Anton Vorontsov: (4 commits)
  kdb: Switch to nolock variants of kmsg_dump functions
  printk: Implement some unlocked kmsg_dump functions
  printk: Remove kdb_syslog_data
  kdb: Revive dmesg command
2012-07-21 10:34:13 -07:00
Anton Vorontsov
c064da4714 kdb: Switch to nolock variants of kmsg_dump functions
The locked variants are prone to deadlocks (suppose we got to the
debugger w/ the logbuf lock held), so let's switch to nolock variants.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-21 10:34:00 -07:00
Anton Vorontsov
533827c921 printk: Implement some unlocked kmsg_dump functions
If used from KDB, the locked variants are prone to deadlocks (suppose we
got to the debugger w/ the logbuf lock held).

So, we have to implement a few routines that grab no logbuf lock.

Yet we don't need these functions in modules, so we don't export them.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-21 10:34:00 -07:00
Anton Vorontsov
1b499d05ee printk: Remove kdb_syslog_data
The function is no longer needed, so remove it.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-21 10:34:00 -07:00
Anton Vorontsov
bc792e612e kdb: Revive dmesg command
The kgdb dmesg command is broken after the printk rework.  The old logic
in kdb code makes no sense in terms of current printk/logging storage
format, and KDB simply hangs forever.

This patch revives the command by switching to kmsg_dumper iterator.

The code is now much more simpler and shorter.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-21 10:34:00 -07:00
Linus Torvalds
eea03c20ae Make wait_for_device_probe() also do scsi_complete_async_scans()
Commit a7a20d1039 ("sd: limit the scope of the async probe domain")
make the SCSI device probing run device discovery in it's own async
domain.

However, as a result, the partition detection was no longer synchronized
by async_synchronize_full() (which, despite the name, only synchronizes
the global async space, not all of them).  Which in turn meant that
"wait_for_device_probe()" would not wait for the SCSI partitions to be
parsed.

And "wait_for_device_probe()" was what the boot time init code relied on
for mounting the root filesystem.

Now, most people never noticed this, because not only is it
timing-dependent, but modern distributions all use initrd.  So the root
filesystem isn't actually on a disk at all.  And then before they
actually mount the final disk filesystem, they will have loaded the
scsi-wait-scan module, which not only does the expected
wait_for_device_probe(), but also does scsi_complete_async_scans().

[ Side note: scsi_complete_async_scans() had also been partially broken,
  but that was fixed in commit 43a8d39d01 ("fix async probe
  regression"), so that same commit a7a20d1039 had actually broken
  setups even if you used scsi-wait-scan explicitly ]

Solve this problem by just moving the scsi_complete_async_scans() call
into wait_for_device_probe().  Everybody who wants to wait for device
probing to finish really wants the SCSI probing to complete, so there's
no reason not to do this.

So now "wait_for_device_probe()" really does what the name implies, and
properly waits for device probing to finish.  This also removes the now
unnecessary extra calls to scsi_complete_async_scans().

Reported-and-tested-by: Artem S. Tashkinov <t.artem@mailcity.com>
Cc: Dan Williams <dan.j.williams@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: James Bottomley <jbottomley@parallels.com>
Cc: Borislav Petkov <bp@amd64.org>
Cc: linux-scsi <linux-scsi@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-18 18:15:46 -07:00
Linus Torvalds
6f70242858 Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
One more time/ntp fix pulled from Ingo Molnar.

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  ntp: Fix STA_INS/DEL clearing bug
2012-07-18 10:36:02 -07:00
Thomas Gleixner
3e997130bd timekeeping: Add missing update call in timekeeping_resume()
The leap second rework unearthed another issue of inconsistent data.

On timekeeping_resume() the timekeeper data is updated, but nothing
calls timekeeping_update(), so now the update code in the timer
interrupt sees stale values.

This has been the case before those changes, but then the timer
interrupt was using stale data as well so this went unnoticed for quite
some time.

Add the missing update call, so all the data is consistent everywhere.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Reported-and-tested-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Reported-and-tested-by: Martin Steigerwald <Martin@lichtvoll.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Linux PM list <linux-pm@vger.kernel.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-16 10:02:17 -07:00
John Stultz
6b1859dba0 ntp: Fix STA_INS/DEL clearing bug
In commit 6b43ae8a61, I
introduced a bug that kept the STA_INS or STA_DEL bit
from being cleared from time_status via adjtimex()
without forcing STA_PLL first.

Usually once the STA_INS is set, it isn't cleared
until the leap second is applied, so its unlikely this
affected anyone. However during testing I noticed it
took some effort to cancel a leap second once STA_INS
was set.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
CC: stable@vger.kernel.org # 3.4
Link: http://lkml.kernel.org/r/1342156917-25092-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-15 09:48:49 +02:00
Linus Torvalds
ab93eb8216 Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU, perf, and scheduler fixes from Ingo Molnar.

The RCU fix is a revert for an optimization that could cause deadlocks.

One of the scheduler commits (164c33c6ad "sched: Fix fork() error path
to not crash") is correct but not complete (some architectures like Tile
are not covered yet) - the resulting additional fixes are still WIP and
Ingo did not want to delay these pending fixes.  See this thread on
lkml:

  [PATCH] fork: fix error handling in dup_task()

The perf fixes are just trivial oneliners.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix segfault with report and mixed guestmount use
  perf kvm: Fix regression with guest machine creation
  perf script: Fix format regression due to libtraceevent merge
  ring-buffer: Fix accounting of entries when removing pages
  ring-buffer: Fix crash due to uninitialized new_pages list head

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  MAINTAINERS/sched: Update scheduler file pattern
  sched/nohz: Rewrite and fix load-avg computation -- again
  sched: Fix fork() error path to not crash
2012-07-14 11:16:24 -07:00
Linus Torvalds
d55e5bd020 Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull the leap second fixes from Thomas Gleixner:
 "It's a rather large series, but well discussed, refined and reviewed.
  It got a massive testing by John, Prarit and tip.

  In theory we could split it into two parts.  The first two patches

    f55a6faa3843: hrtimer: Provide clock_was_set_delayed()
    4873fa070ae8: timekeeping: Fix leapsecond triggered load spike issue

  are merely preventing the stuff loops forever issues, which people
  have observed.

  But there is no point in delaying the other 4 commits which achieve
  full correctness into 3.6 as they are tagged for stable anyway.  And I
  rather prefer to have the full fixes merged in bulk than a "prevent
  the observable wreckage and deal with the hidden fallout later"
  approach."

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimer: Update hrtimer base offsets each hrtimer_interrupt
  timekeeping: Provide hrtimer update function
  hrtimers: Move lock held region in hrtimer_interrupt()
  timekeeping: Maintain ktime_t based offsets for hrtimers
  timekeeping: Fix leapsecond triggered load spike issue
  hrtimer: Provide clock_was_set_delayed()
2012-07-13 15:31:21 -07:00
Linus Torvalds
00c3e276c5 Merge branch 'akpm' (Andrew's patch-bomb)
Merge random patches from Andrew Morton.

* Merge emailed patches from Andrew Morton <akpm@linux-foundation.org>: (32 commits)
  memblock: free allocated memblock_reserved_regions later
  mm: sparse: fix usemap allocation above node descriptor section
  mm: sparse: fix section usemap placement calculation
  xtensa: fix incorrect memset
  shmem: cleanup shmem_add_to_page_cache
  shmem: fix negative rss in memcg memory.stat
  tmpfs: revert SEEK_DATA and SEEK_HOLE
  drivers/rtc/rtc-twl.c: fix threaded IRQ to use IRQF_ONESHOT
  fat: fix non-atomic NFS i_pos read
  MAINTAINERS: add OMAP CPUfreq driver to OMAP Power Management section
  sgi-xp: nested calls to spin_lock_irqsave()
  fs: ramfs: file-nommu: add SetPageUptodate()
  drivers/rtc/rtc-mxc.c: fix irq enabled interrupts warning
  mm/memory_hotplug.c: release memory resources if hotadd_new_pgdat() fails
  h8300/uaccess: add mising __clear_user()
  h8300/uaccess: remove assignment to __gu_val in unhandled case of get_user()
  h8300/time: add missing #include <asm/irq_regs.h>
  h8300/signal: fix typo "statis"
  h8300/pgtable: add missing #include <asm-generic/pgtable.h>
  drivers/rtc/rtc-ab8500.c: ensure correct probing of the AB8500 RTC when Device Tree is enabled
  ...
2012-07-11 16:06:54 -07:00
Konstantin Khlebnikov
4229fb1dc6 c/r: prctl: less paranoid prctl_set_mm_exe_file()
"no other files mapped" requirement from my previous patch (c/r: prctl:
update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal) is too
paranoid, it forbids operation even if there mapped one shared-anon vma.

Let's check that current mm->exe_file already unmapped, in this case
exe_file symlink already outdated and its changing is reasonable.

Plus, this patch fixes exit code in case operation success.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-11 16:04:43 -07:00
John Stultz
5baefd6d84 hrtimer: Update hrtimer base offsets each hrtimer_interrupt
The update of the hrtimer base offsets on all cpus cannot be made
atomically from the timekeeper.lock held and interrupt disabled region
as smp function calls are not allowed there.

clock_was_set(), which enforces the update on all cpus, is called
either from preemptible process context in case of do_settimeofday()
or from the softirq context when the offset modification happened in
the timer interrupt itself due to a leap second.

In both cases there is a race window for an hrtimer interrupt between
dropping timekeeper lock, enabling interrupts and clock_was_set()
issuing the updates. Any interrupt which arrives in that window will
see the new time but operate on stale offsets.

So we need to make sure that an hrtimer interrupt always sees a
consistent state of time and offsets.

ktime_get_update_offsets() allows us to get the current monotonic time
and update the per cpu hrtimer base offsets from hrtimer_interrupt()
to capture a consistent state of monotonic time and the offsets. The
function replaces the existing ktime_get() calls in hrtimer_interrupt().

The overhead of the new function vs. ktime_get() is minimal as it just
adds two store operations.

This ensures that any changes to realtime or boottime offsets are
noticed and stored into the per-cpu hrtimer base structures, prior to
any hrtimer expiration and guarantees that timers are not expired early.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1341960205-56738-8-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:39 +02:00
Thomas Gleixner
f6c06abfb3 timekeeping: Provide hrtimer update function
To finally fix the infamous leap second issue and other race windows
caused by functions which change the offsets between the various time
bases (CLOCK_MONOTONIC, CLOCK_REALTIME and CLOCK_BOOTTIME) we need a
function which atomically gets the current monotonic time and updates
the offsets of CLOCK_REALTIME and CLOCK_BOOTTIME with minimalistic
overhead. The previous patch which provides ktime_t offsets allows us
to make this function almost as cheap as ktime_get() which is going to
be replaced in hrtimer_interrupt().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:39 +02:00
Thomas Gleixner
196951e912 hrtimers: Move lock held region in hrtimer_interrupt()
We need to update the base offsets from this code and we need to do
that under base->lock. Move the lock held region around the
ktime_get() calls. The ktime_get() calls are going to be replaced with
a function which gets the time and the offsets atomically.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/1341960205-56738-6-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:38 +02:00
Thomas Gleixner
5b9fe759a6 timekeeping: Maintain ktime_t based offsets for hrtimers
We need to update the hrtimer clock offsets from the hrtimer interrupt
context. To avoid conversions from timespec to ktime_t maintain a
ktime_t based representation of those offsets in the timekeeper. This
puts the conversion overhead into the code which updates the
underlying offsets and provides fast accessible values in the hrtimer
interrupt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1341960205-56738-4-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:38 +02:00
John Stultz
4873fa070a timekeeping: Fix leapsecond triggered load spike issue
The timekeeping code misses an update of the hrtimer subsystem after a
leap second happened. Due to that timers based on CLOCK_REALTIME are
either expiring a second early or late depending on whether a leap
second has been inserted or deleted until an operation is initiated
which causes that update. Unless the update happens by some other
means this discrepancy between the timekeeping and the hrtimer data
stays forever and timers are expired either early or late.

The reported immediate workaround - $ data -s "`date`" - is causing a
call to clock_was_set() which updates the hrtimer data structures.
See: http://www.sheeri.com/content/mysql-and-leap-second-high-cpu-and-fix

Add the missing clock_was_set() call to update_wall_time() in case of
a leap second event. The actual update is deferred to softirq context
as the necessary smp function call cannot be invoked from hard
interrupt context.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Reported-by: Jan Engelhardt <jengelh@inai.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:37 +02:00
John Stultz
f55a6faa38 hrtimer: Provide clock_was_set_delayed()
clock_was_set() cannot be called from hard interrupt context because
it calls on_each_cpu().

For fixing the widely reported leap seconds issue it is necessary to
call it from hard interrupt context, i.e. the timer tick code, which
does the timekeeping updates.

Provide a new function which denotes it in the hrtimer cpu base
structure of the cpu on which it is called and raise the hrtimer
softirq. We then execute the clock_was_set() notificiation from
softirq context in run_hrtimer_softirq(). The hrtimer softirq is
rarely used, so polling the flag there is not a performance issue.

[ tglx: Made it depend on CONFIG_HIGH_RES_TIMERS. We really should get
  rid of all this ifdeffery ASAP ]

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Reported-by: Jan Engelhardt <jengelh@inai.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1341960205-56738-2-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-07-11 23:34:37 +02:00
Linus Torvalds
3dc352c02f printk fixes for 3.5-rc6
Here are some more printk fixes for 3.5-rc6.  They resolve all known
 outstanding issues with the printk changes that have been happening.  They have
 been tested by the people reporting the problems.
 
 This hopefully should be it for the printk stuff for 3.5-final.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull printk fixes from Greg Kroah-Hartman:
 "Here are some more printk fixes for 3.5-rc6.  They resolve all known
  outstanding issues with the printk changes that have been happening.
  They have been tested by the people reporting the problems.

  This hopefully should be it for the printk stuff for 3.5-final.

  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>"

* tag 'driver-core-3.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  kmsg: merge continuation records while printing
  kmsg: /proc/kmsg - support reading of partial log records
  kmsg: make sure all messages reach a newly registered boot console
  kmsg: properly handle concurrent non-blocking read() from /proc/kmsg
  kmsg: add the facility number to the syslog prefix
  kmsg: escape the backslash character while exporting data
  printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irq
2012-07-11 12:15:15 -07:00
Kay Sievers
5becfb1df5 kmsg: merge continuation records while printing
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>
2012-07-09 12:15:42 -07:00
Kay Sievers
eb02dac937 kmsg: /proc/kmsg - support reading of partial log records
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>
2012-07-09 10:05:10 -07:00
Tejun Heo
5db9a4d99b cgroup: fix cgroup hierarchy umount race
48ddbe1946 "cgroup: make css->refcnt clearing on cgroup removal
optional" allowed a css to linger after the associated cgroup is
removed.  As a css holds a reference on the cgroup's dentry, it means
that cgroup dentries may linger for a while.

Destroying a superblock which has dentries with positive refcnts is a
critical bug and triggers BUG() in vfs code.  As each cgroup dentry
holds an s_active reference, any lingering cgroup has both its dentry
and the superblock pinned and thus preventing premature release of
superblock.

Unfortunately, after 48ddbe1946, there's a small window while
releasing a cgroup which is directly under the root of the hierarchy.
When a cgroup directory is released, vfs layer first deletes the
corresponding dentry and then invokes dput() on the parent, which may
recurse further, so when a cgroup directly below root cgroup is
released, the cgroup is first destroyed - which releases the s_active
it was holding - and then the dentry for the root cgroup is dput().

This creates a window where the root dentry's refcnt isn't zero but
superblock's s_active is.  If umount happens before or during this
window, vfs will see the root dentry with non-zero refcnt and trigger
BUG().

Before 48ddbe1946, this problem didn't exist because the last dentry
reference was guaranteed to be put synchronously from rmdir(2)
invocation which holds s_active around the whole process.

Fix it by holding an extra superblock->s_active reference across
dput() from css release, which is the dput() path added by 48ddbe1946
and the only one which doesn't hold an extra s_active ref across the
final cgroup dput().

Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4FEEA5CB.8070809@huawei.com>
Reported-by: shyju pv <shyju.pv@huawei.com>
Tested-by: shyju pv <shyju.pv@huawei.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Li Zefan <lizefan@huawei.com>
2012-07-07 16:08:18 -07:00
Tejun Heo
7db5b3ca0e Revert "cgroup: superblock can't be released with active dentries"
This reverts commit fa980ca87d.  The
commit was an attempt to fix a race condition where a cgroup hierarchy
may be unmounted with positive dentry reference on root cgroup.  While
the commit made the race condition slightly more difficult to trigger,
the race was still there and could be reliably triggered using a
different test case.

Revert the incorrect fix.  The next commit will describe the race and
fix it correctly.

Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4FEEA5CB.8070809@huawei.com>
Reported-by: shyju pv <shyju.pv@huawei.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Li Zefan <lizefan@huawei.com>
2012-07-07 15:55:47 -07:00
Kay Sievers
68b6507dc5 kmsg: make sure all messages reach a newly registered boot console
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>
2012-07-06 09:50:09 -07:00
Kay Sievers
cb424ffe9f kmsg: properly handle concurrent non-blocking read() from /proc/kmsg
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>
2012-07-06 09:50:09 -07:00
Kay Sievers
43a73a50b3 kmsg: add the facility number to the syslog prefix
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>
2012-07-06 09:50:09 -07:00
Kay Sievers
e3f5a5f271 kmsg: escape the backslash character while exporting data
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>
2012-07-06 09:50:09 -07:00
liu chuansheng
5c53d819c7 printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irq
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>
2012-07-06 09:50:08 -07:00
Ingo Molnar
40b3c43f04 Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent
Pull low probability CONFIG_RCU_BOOST=y deadlock fix from Paul E. McKenney.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-06 11:18:50 +02:00
Peter Zijlstra
5167e8d541 sched/nohz: Rewrite and fix load-avg computation -- again
Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies <dsmythies@telus.net>
Reported-and-tested-by: Charles Wang <muming.wq@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-05 20:58:13 +02:00
Salman Qazi
164c33c6ad sched: Fix fork() error path to not crash
In dup_task_struct(), if arch_dup_task_struct() fails, the clean up
code fails to clean up correctly.  That's because the clean up
code depends on unininitalized ti->task pointer.  We fix this
by making sure that the task and thread_info know about each other
before we attempt to take the error path.

Signed-off-by: Salman Qazi <sqazi@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120626011815.11323.5533.stgit@dungbeetle.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-05 20:57:32 +02:00
Linus Torvalds
a3da2c6913 Merge branch 'for-linus' of git://git.kernel.dk/linux-block
Pull block bits from Jens Axboe:
 "As vacation is coming up, thought I'd better get rid of my pending
  changes in my for-linus branch for this iteration.  It contains:

   - Two patches for mtip32xx.  Killing a non-compliant sysfs interface
     and moving it to debugfs, where it belongs.

   - A few patches from Asias.  Two legit bug fixes, and one killing an
     interface that is no longer in use.

   - A patch from Jan, making the annoying partition ioctl warning a bit
     less annoying, by restricting it to !CAP_SYS_RAWIO only.

   - Three bug fixes for drbd from Lars Ellenberg.

   - A fix for an old regression for umem, it hasn't really worked since
     the plugging scheme was changed in 3.0.

   - A few fixes from Tejun.

   - A splice fix from Eric Dumazet, fixing an issue with pipe
     resizing."

* 'for-linus' of git://git.kernel.dk/linux-block:
  scsi: Silence unnecessary warnings about ioctl to partition
  block: Drop dead function blk_abort_queue()
  block: Mitigate lock unbalance caused by lock switching
  block: Avoid missed wakeup in request waitqueue
  umem: fix up unplugging
  splice: fix racy pipe->buffers uses
  drbd: fix null pointer dereference with on-congestion policy when diskless
  drbd: fix list corruption by failing but already aborted reads
  drbd: fix access of unallocated pages and kernel panic
  xen/blkfront: Add WARN to deal with misbehaving backends.
  blkcg: drop local variable @q from blkg_destroy()
  mtip32xx: Create debugfs entries for troubleshooting
  mtip32xx: Remove 'registers' and 'flags' from sysfs
  blkcg: fix blkg_alloc() failure path
  block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHED
  block: fix return value on cfq_init() failure
  mtip32xx: Remove version.h header file inclusion
  xen/blkback: Copy id field when doing BLKIF_DISCARD.
2012-07-03 15:45:10 -07:00
Paul E. McKenney
cba6d0d64e Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"
This reverts commit 616c310e83.
(Move PREEMPT_RCU preemption to switch_to() invocation).
Testing by Sasha Levin <levinsasha928@gmail.com> showed that this
can result in deadlock due to invoking the scheduler when one of
the runqueue locks is held.  Because this commit was simply a
performance optimization, revert it.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
2012-07-02 11:39:19 -07:00
Randy Dunlap
4f0f4af59c printk.c: fix kernel-doc warnings
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>
2012-06-30 15:56:40 -07:00
Linus Torvalds
21f27291f5 Driver Core fixes for 3.5-rc5
Here is a number of printk() fixes, specifically a few reported by the
 crazy blog program that ships in SUSE releases (that's "boot log" and
 not "web log", it predates the general "blog" terminology by many
 years), and the restoration of the continuation line functionality
 reported by Stephen and others.  Yes, the changes seem a bit big this
 late in the cycle, but I've been beating on them for a while now, and
 Stephen has even optimized it a bit, so all looks good to me.
 
 The other change in here is a Documentation update for the stable kernel
 rules describing how some distro patches should be backported, to
 hopefully drive a bit more response from the distros to the stable
 kernel releases.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver Core fixes from Greg Kroah-Hartman:
 "Here is a number of printk() fixes, specifically a few reported by the
  crazy blog program that ships in SUSE releases (that's "boot log" and
  not "web log", it predates the general "blog" terminology by many
  years), and the restoration of the continuation line functionality
  reported by Stephen and others.  Yes, the changes seem a bit big this
  late in the cycle, but I've been beating on them for a while now, and
  Stephen has even optimized it a bit, so all looks good to me.

  The other change in here is a Documentation update for the stable
  kernel rules describing how some distro patches should be backported,
  to hopefully drive a bit more response from the distros to the stable
  kernel releases.

  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>"

* tag 'driver-core-3.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  printk: Optimize if statement logic where newline exists
  printk: flush continuation lines immediately to console
  syslog: fill buffer with more than a single message for SYSLOG_ACTION_READ
  Revert "printk: return -EINVAL if the message len is bigger than the buf size"
  printk: fix regression in SYSLOG_ACTION_CLEAR
  stable: Allow merging of backports for serious user-visible performance issues
2012-06-30 10:11:24 -07:00
Steven Rostedt
d36208227d printk: Optimize if statement logic where newline exists
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>
2012-06-29 16:55:35 -04:00
Vaibhav Nagarnaik
48fdc72f23 ring-buffer: Fix accounting of entries when removing pages
When removing pages from the ring buffer, its state is not reset. This
means that the counters need to be correctly updated to account for the
pages removed.

Update the overrun counter to reflect the removed events from the pages.

Link: http://lkml.kernel.org/r/1340998301-1715-1-git-send-email-vnagarnaik@google.com

Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-06-29 16:17:17 -04:00
Vaibhav Nagarnaik
44b99462d9 ring-buffer: Fix crash due to uninitialized new_pages list head
The new_pages list head in the cpu_buffer is not initialized. When
adding pages to the ring buffer, if the memory allocation fails in
ring_buffer_resize, the clean up handler tries to free up the allocated
pages from all the cpu buffers. The panic is caused by referencing the
uninitialized new_pages list head.

Initializing the new_pages list head in rb_allocate_cpu_buffer fixes
this.

Link: http://lkml.kernel.org/r/1340391005-10880-1-git-send-email-vnagarnaik@google.com

Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-06-29 16:16:35 -04:00
Kay Sievers
084681d14e printk: flush continuation lines immediately to console
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>
2012-06-29 11:39:42 -04:00
Jan Beulich
116e90b23f syslog: fill buffer with more than a single message for SYSLOG_ACTION_READ
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>
2012-06-26 12:37:36 -07:00
Greg Kroah-Hartman
6fda135c90 Revert "printk: return -EINVAL if the message len is bigger than the buf size"
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>
2012-06-26 12:35:24 -07:00
Paul E. McKenney
b41772abeb rcu: Stop rcu_do_batch() from multiplexing the "count" variable
Commit b1420f1c (Make rcu_barrier() less disruptive) rearranged the
code in rcu_do_batch(), moving the ->qlen manipulation to follow
the requeueing of the callbacks.  Unfortunately, this rearrangement
clobbered the value of the "count" local variable before the value
of rdp->qlen was adjusted, resulting in the value of rdp->qlen being
inaccurate.  This commit therefore introduces an index variable "i",
avoiding the inadvertent multiplexing.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-06-25 12:35:25 -07:00
Alan Stern
4661e3568a printk: fix regression in SYSLOG_ACTION_CLEAR
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>
2012-06-25 12:11:58 -07:00
Linus Torvalds
a11637194a Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf updates from Ingo Molnar.

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  ftrace: Make all inline tags also include notrace
  perf: Use css_tryget() to avoid propping up css refcount
  perf tools: Fix synthesizing tracepoint names from the perf.data headers
  perf stat: Fix default output file
  perf tools: Fix endianity swapping for adds_features bitmask
2012-06-22 10:58:57 -07:00
Linus Torvalds
2ce5682947 Merge branch 'for-3.5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull two cgroup fixes from Tejun Heo:
 "This containes two patches fixing a refcnt race bug during css_put().
  Decrementing and checking the value weren't atomic and two tasks could
  think that they both pushed the counter to zero."

* 'for-3.5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroups: Account for CSS_DEACT_BIAS in __css_put
  cgroup: make sure that decisions in __css_put are atomic
2012-06-20 22:11:04 -07:00
Linus Torvalds
fe80352460 Driver core and printk fixes for 3.5-rc4
Here are some fixes for 3.5-rc4 that resolve the kmsg problems that
 people have reported showing up after the printk and kmsg changes went
 into 3.5-rc1.  There are also a smattering of other tiny fixes for the
 extcon and hyper-v drivers that people have reported.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.5-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core and printk fixes from Greg Kroah-Hartman:
 "Here are some fixes for 3.5-rc4 that resolve the kmsg problems that
  people have reported showing up after the printk and kmsg changes went
  into 3.5-rc1.  There are also a smattering of other tiny fixes for the
  extcon and hyper-v drivers that people have reported.

  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>"

* tag 'driver-core-3.5-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  extcon: max8997: Add missing kfree for info->edev in max8997_muic_remove()
  extcon: Set platform drvdata in gpio_extcon_probe() and fix irq leak
  extcon: Fix wrong index in max8997_extcon_cable[]
  kmsg - kmsg_dump() fix CONFIG_PRINTK=n compilation
  printk: return -EINVAL if the message len is bigger than the buf size
  printk: use mutex lock to stop syslog_seq from going wild
  kmsg - kmsg_dump() use iterator to receive log buffer content
  vme: change maintainer e-mail address
  Extcon: Don't try to create duplicate link names
  driver core: fixup reversed deferred probe order
  printk: Fix alignment of buf causing crash on ARM EABI
  Tools: hv: verify origin of netlink connector message
2012-06-20 15:14:28 -07:00
Cyrill Gorcunov
5702c5eeab c/r: prctl: Move PR_GET_TID_ADDRESS to a proper place
During merging of PR_GET_TID_ADDRESS patch the code has been misplaced (it
happened to appear under PR_MCE_KILL) in result noone can use this option.

Fix it by moving code snippet to a proper place.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-20 14:39:36 -07:00
Oleg Nesterov
50d75f8dae pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
find_new_reaper() changes pid_ns->child_reaper, see add0d4df ("pid_ns:
zap_pid_ns_processes: fix the ->child_reaper changing").

The original reason has gone away after the previous patch, ->children
list must be empty after zap_pid_ns_processes().

However now we can not switch to init_pid_ns.child_reaper.
__unhash_process() relies on the "->child_reaper == parent" check, but
this check does not work if the last exiting task is also the child
reaper.

As Eric sugested, we can change __unhash_process() to use the parent's
pid_ns and remove this code.

Also, with this change we can move detach_pid(PIDTYPE_PID) back, where it
was before the previous fix.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Louis Rilling <louis.rilling@kerlabs.com>
Cc: Mike Galbraith <efault@gmx.de>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Tested-by: Andrew Wagin <avagin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-20 14:39:36 -07:00
Eric W. Biederman
6347e90091 pidns: guarantee that the pidns init will be the last pidns process reaped
Today we have a twofold bug.  Sometimes release_task on pid == 1 in a pid
namespace can run before other processes in a pid namespace have had
release task called.  With the result that pid_ns_release_proc can be
called before the last proc_flus_task() is done using upid->ns->proc_mnt,
resulting in the use of a stale pointer.  This same set of circumstances
can lead to waitpid(...) returning for a processes started with
clone(CLONE_NEWPID) before the every process in the pid namespace has
actually exited.

To fix this modify zap_pid_ns_processess wait until all other processes in
the pid namespace have exited, even EXIT_DEAD zombies.

The delay_group_leader and related tests ensure that the thread gruop
leader will be the last thread of a process group to be reaped, or to
become EXIT_DEAD and self reap.  With the change to zap_pid_ns_processes
we get the guarantee that pid == 1 in a pid namespace will be the last
task that release_task is called on.

With pid == 1 being the last task to pass through release_task
pid_ns_release_proc can no longer be called too early nor can wait return
before all of the EXIT_DEAD tasks in a pid namespace have exited.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <louis.rilling@kerlabs.com>
Cc: Mike Galbraith <efault@gmx.de>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Tested-by: Andrew Wagin <avagin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-20 14:39:36 -07:00