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From: Nikita Danilov <Nikita@Namesys.COM>
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To: Dawson Engler <engler@csl.stanford.edu>
Cc: akpm@digeo.com (Andrew Morton), linux-kernel@vger.kernel.org
Subject: Re: [CHECKER] potential deadlocks
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	<200303040752.h247qOx20275@csl.stanford.edu>
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Dawson Engler writes:
 > > Andrew Morton writes:

[...]

Sorry for delay.

 > 
 > Do you mean calls to copy_*_user and kmalloc(GFP_WAIT) or did you have
 > something else in mind as well?

Yes. Imagine thread that tries to allocate memory with __GFP_FS while
keeping some file system locks. Now try_to_free_pages() calls
->writepage() method that tries to acquire the same lock. See, for
examples, comment before fs/ext3/inode.c:ext3_writepage(), or in
fs/dcache.c:shrink_dcache_memory().

 > 
 > > We have (incomplete) description of kernel lock ordering, which is
 > > centered around reiser4 locks, but also includes some core kernel stuff.
 > > 
 > > It is available at 
 > > 
 > > http://www.namesys.com/v4/lock-ordering.dot  --- source for Bell-Labs' dot(1)
 > > http://www.namesys.com/v4/lock-ordering.ps   --- postscript output, produced from the .dot source
 > 
 > Wonderful; thanks!
 > 

I would be glad to receive additions and corrections for this diagram.

 > 
 > 
 > 

Nikita.
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