BUG? a suspected race bug at cleaner_kthread()

BUG? a suspected race bug at cleaner_kthread()

[홍신 shin hong]

Hello. I am reporting a suspected race bug at cleaner_kthread()
in btrfs/disk-io.c of Linux 2.6.30.4.

I hope this report is helpful. Please examine the report and
please let me know your opinion.

clear_ktherad() is spawned as a thread by open_ctree().

The function is finished if kthread_should_stop() or
root->fs_info->closing becomes non-zero.

If clear_kthread() is finished before other thread invoke
kthread_stop() for clear_kthread(),
the caller of kthread_stop() might have problem (waiting indefinitely).

It seems that close_ctree() set fs_info->closing
and then kthread_stop(root->fs_info->cleaner_kthread)
so that it might result this type of error.

Thank you

Sincerely
Shin Hong

Re: BUG? a suspected race bug at cleaner_kthread()

[Yan, Zheng]

2009/9/3 =ED=99=8D=EC=8B=A0 shin hong <hongshin@gmail.com>:
> Hello. I am reporting a suspected race bug at cleaner_kthread()
> in btrfs/disk-io.c of Linux 2.6.30.4.
>
> I hope this report is helpful. Please examine the report and
> please let me know your opinion.
>
> clear_ktherad() is spawned as a thread by open_ctree().
>
> The function is finished if kthread_should_stop() or
> root->fs_info->closing becomes non-zero.
>
> If clear_kthread() is finished before other thread invoke
> kthread_stop() for clear_kthread(),
> the caller of kthread_stop() might have problem (waiting indefinitely=
).
>
> It seems that close_ctree() set fs_info->closing
> and then kthread_stop(root->fs_info->cleaner_kthread)
> so that it might result this type of error.
>

You are right. Would you please send a patch.

Note: there is similar bug in transaction_kthread.

Yan, Zheng
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