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    • Hugh Dickins's avatar
      cgroup: fix rmdir EBUSY regression in 3.11 · bb78a92f
      Hugh Dickins authored 
      

On 3.11-rc we are seeing cgroup directories left behind when they should
have been removed.  Here's a trivial reproducer:

cd /sys/fs/cgroup/memory
mkdir parent parent/child; rmdir parent/child parent
rmdir: failed to remove `parent': Device or resource busy

It's because cgroup_destroy_locked() (step 1 of destruction) leaves
cgroup on parent's children list, letting cgroup_offline_fn() (step 2 of
destruction) remove it; but step 2 is run by work queue, which may not
yet have removed the children when parent destruction checks the list.

Fix that by checking through a non-empty list of children: if every one
of them has already been marked CGRP_DEAD, then it's safe to proceed:
those children are invisible to userspace, and should not obstruct rmdir.

(I didn't see any reason to keep the cgrp->children checks under the
unrelated css_set_lock, so moved them out.)

tj: Flattened nested ifs a bit and updated comment so that it's
    correct on both for-3.11-fixes and for-3.12.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      bb78a92f
    • Tejun Heo's avatar
      workqueue: cond_resched() after processing each work item · b22ce278
      Tejun Heo authored 
      

If !PREEMPT, a kworker running work items back to back can hog CPU.
This becomes dangerous when a self-requeueing work item which is
waiting for something to happen races against stop_machine.  Such
self-requeueing work item would requeue itself indefinitely hogging
the kworker and CPU it's running on while stop_machine would wait for
that CPU to enter stop_machine while preventing anything else from
happening on all other CPUs.  The two would deadlock.

Jamie Liu reports that this deadlock scenario exists around
scsi_requeue_run_queue() and libata port multiplier support, where one
port may exclude command processing from other ports.  With the right
timing, scsi_requeue_run_queue() can end up requeueing itself trying
to execute an IO which is asked to be retried while another device has
an exclusive access, which in turn can't make forward progress due to
stop_machine.

Fix it by invoking cond_resched() after executing each work item.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarJamie Liu <jamieliu@google.com>
References: http://thread.gmane.org/gmane.linux.kernel/1552567
Cc: stable@vger.kernel.org
--
 kernel/workqueue.c |    9 +++++++++
 1 file changed, 9 insertions(+)
      b22ce278
    • Linus Torvalds's avatar
      Merge branch 'akpm' (patches from Andrew Morton) · c95389b4
      Linus Torvalds authored 
      Merge fixes from Andrew Morton:
 "Five fixes.

  err, make that six.  let me try again"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  fs/ocfs2/super.c: Use bigger nodestr to accomodate 32-bit node numbers
  memcg: check that kmem_cache has memcg_params before accessing it
  drivers/base/memory.c: fix show_mem_removable() to handle missing sections
  IPC: bugfix for msgrcv with msgtyp < 0
  Omnikey Cardman 4000: pull in ioctl.h in user header
  timer_list: correct the iterator for timer_list
      c95389b4
    • Goldwyn Rodrigues's avatar
      fs/ocfs2/super.c: Use bigger nodestr to accomodate 32-bit node numbers · 49fa8140
      Goldwyn Rodrigues authored 
      

While using pacemaker/corosync, the node numbers are generated using IP
address as opposed to serial node number generation.  This may not fit
in a 8-byte string.  Use a bigger string to print the complete node
number.

Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      49fa8140
    • Andrey Vagin's avatar
      memcg: check that kmem_cache has memcg_params before accessing it · 6f6b8951
      Andrey Vagin authored 
      If the system had a few memory groups and all of them were destroyed,
memcg_limited_groups_array_size has non-zero value, but all new caches
are created without memcg_params, because memcg_kmem_enabled() returns
false.

We try to enumirate child caches in a few places and all of them are
potentially dangerous.

For example my kernel is compiled with CONFIG_SLAB and it crashed when I
tryed to mount a NFS share after a few experiments with kmemcg.

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  IP: [<ffffffff8118166a>] do_tune_cpucache+0x8a/0xd0
  PGD b942a067 PUD b999f067 PMD 0
  Oops: 0000 [#1] SMP
  Modules linked in: fscache(+) ip6table_filter ip6_tables iptable_filter ip_tables i2c_piix4 pcspkr virtio_net virtio_balloon i2c_core floppy
  CPU: 0 PID: 357 Comm: modprobe Not tainted 3.11.0-rc7+ #59
  Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  task: ffff8800b9f98240 ti: ffff8800ba32e000 task.ti: ffff88...
      6f6b8951