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Date: Wed, 22 Jul 2009 09:42:41 +0800 From: Danny Feng <dfeng@...hat.com> To: Li Zefan <lizf@...fujitsu.com> CC: balbir@...ux.vnet.ibm.com, Zefan Li <lizf.kernel@...il.com>, menage@...gle.com, containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] cgroup: fix reverse unlock sequence in cgroup_get_sb On 07/22/2009 08:53 AM, Li Zefan wrote: >>>> Seems reasonable to me. You might also want to mention that elsewhere >>>> the sequence is unlock cgroup_mutex followed by inode->i_mutex. >>>> >>>> Acked-by: Balbir Singh balbir@...ux.vnet.ibm.com >>>> >>> No, the unlock order is irrelevant. It's the lock order that matters. So >>> this patch >>> fixes nothing. >>> >>> Xiaotian, you didn't run into deadlock, did you? >>> >>> >> Li, Consider the following >> >> >> lock(A) >> lock(B) >> unlock(A) >> unlock(B) >> >> Tomorrow if a unsuspecting programmer does this >> >> lock(A) >> lock(B) >> unlock(A) >> >> code block >> >> unlock(B) >> >> >> What protects code block? lock B? Is that the intention? >> >> > > I won't worry about that. If unlock order is a concern, > we should have taught lockdep to detect it. > > Here's a reply from Linus on this issue: > > http://lkml.org/lkml/2008/10/8/150 > OK, this patch is trivial. Just for consistency with previous unlock sequence:-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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