a suspected race at __posix_lock_file()

a suspected race at __posix_lock_file()

[홍신 shin hong]

Hi. I found a suspected race condition bug at fs/locks/__posix_lock_file()
in recent Linux kernel.

This bug is similar to the one reported in ChangeLog 2.6.24 ( commit
85c59580b30c82aa771aa33b37217a6b6851bc14 ).

Big Kernel Lock(BKL) might be released and re-taken
at the call site of locks_delete_lock()
since Releasing-On-Block semantics of BKL.
Locks_delete_lock() may be blocked by kmem_cache_alloc() invocation.

Please examine the possbility of race condition of this code
and let me know your opinion.

Re: a suspected race at __posix_lock_file()

[Matthew Wilcox]

On Fri, Jul 24, 2009 at 02:56:24PM +0900, ?????? shin hong wrote:
> Hi. I found a suspected race condition bug at fs/locks/__posix_lock_file()
> in recent Linux kernel.
> 
> This bug is similar to the one reported in ChangeLog 2.6.24 ( commit
> 85c59580b30c82aa771aa33b37217a6b6851bc14 ).
> 
> Big Kernel Lock(BKL) might be released and re-taken
> at the call site of locks_delete_lock()
> since Releasing-On-Block semantics of BKL.
> Locks_delete_lock() may be blocked by kmem_cache_alloc() invocation.

Could you explain to me how locks_delete_lock() calls kmem_cache_alloc()?

> Please examine the possbility of race condition of this code
> and let me know your opinion.
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-- 
Matthew Wilcox				Intel Open Source Technology Centre
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