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workqueue: exit rescuer_thread() as TASK_RUNNING
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A rescue thread exiting TASK_INTERRUPTIBLE can lead to a task scheduling
off, never to be seen again.  In the case where this occurred, an exiting
thread hit reiserfs homebrew conditional resched while holding a mutex,
bringing the box to its knees.

PID: 18105  TASK: ffff8807fd412180  CPU: 5   COMMAND: "kdmflush"
 #0 [ffff8808157e7670] schedule at ffffffff8143f489
 #1 [ffff8808157e77b8] reiserfs_get_block at ffffffffa038ab2d [reiserfs]
 #2 [ffff8808157e79a8] __block_write_begin at ffffffff8117fb14
 #3 [ffff8808157e7a98] reiserfs_write_begin at ffffffffa0388695 [reiserfs]
 #4 [ffff8808157e7ad8] generic_perform_write at ffffffff810ee9e2
 #5 [ffff8808157e7b58] generic_file_buffered_write at ffffffff810eeb41
 torvalds#6 [ffff8808157e7ba8] __generic_file_aio_write at ffffffff810f1a3a
 torvalds#7 [ffff8808157e7c58] generic_file_aio_write at ffffffff810f1c88
 torvalds#8 [ffff8808157e7cc8] do_sync_write at ffffffff8114f850
 torvalds#9 [ffff8808157e7dd8] do_acct_process at ffffffff810a268f
    [exception RIP: kernel_thread_helper]
    RIP: ffffffff8144a5c0  RSP: ffff8808157e7f58  RFLAGS: 00000202
    RAX: 0000000000000000  RBX: 0000000000000000  RCX: 0000000000000000
    RDX: 0000000000000000  RSI: ffffffff8107af60  RDI: ffff8803ee491d18
    RBP: 0000000000000000   R8: 0000000000000000   R9: 0000000000000000
    R10: 0000000000000000  R11: 0000000000000000  R12: 0000000000000000
    R13: 0000000000000000  R14: 0000000000000000  R15: 0000000000000000
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018

Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
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@htejun
Mike Galbraith authored and htejun committed Dec 1, 2012
1 parent b3c3a9c commit 412d32e
Showing 1 changed file with 3 additions and 1 deletion.
4 changes: 3 additions & 1 deletion kernel/workqueue.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2407,8 +2407,10 @@ static int rescuer_thread(void *__wq)
repeat:
set_current_state(TASK_INTERRUPTIBLE);

if (kthread_should_stop())
if (kthread_should_stop()) {
__set_current_state(TASK_RUNNING);
return 0;
}

/*
* See whether any cpu is asking for help. Unbounded
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