linux-kernel - Re: 2.6.26-rc4: RIP __call_for_each

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Message-ID: <alpine.LFD.1.10.0806041129570.3473@woody.linux-foundation.org>
Date:	Wed, 4 Jun 2008 11:32:03 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	torvalds@...uxfoundation.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.26-rc4: RIP __call_for_each_cic+0x20/0x50



On Tue, 3 Jun 2008, Paul E. McKenney wrote:
> 
> The fact that put_io_context() was called from exit_io_context() means
> that this is the last thread of a process exiting.  The fact that
> cfq_free_io_context() was called (via cfq_dtor()) from put_io_context()
> means that this was the last reference to the io_context.  Yet when
> we traverse the cic_list, part of it is corrupted -- ascii "k"s through
> RAX and RBX.

The "ascii 'k's" are just the slab POISON_FREE byte (0x6b).

IOW, something simply kfree'd the memory too early, causing the list 
traversal to then break.

		Linus
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