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SubjectRe: [PATCH block/for-3.3/core] block: an exiting task should be allowed to create io_context
On 2012-01-03 21:09, Tejun Heo wrote:
> On Tue, Jan 03, 2012 at 09:59:22AM -0800, Tejun Heo wrote:
>> That should have been service tree. I couldn't find more missing
>> removals other than the one Shaohua's patch already fixed. Close
>> cooperator selection in cfq_select_queue() seems suspicious tho. I
>> can't see what prevents it from returning an empty coopeator cfqq.
>> I'm trying to verify whether that's the case. Will update when I know
>> more.
>
> While testing, found another bug.
>
> Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
> Last user: [<ffffffff813a82ee>](cfq_put_queue+0x7e/0xd0)
> 070: e8 32 ab 1d 00 88 ff ff e8 32 ab 1d 00 88 ff ff .2.......2......
> Prev obj: start=ffff88001dab3178, len=232
> Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
> Last user: [<ffffffff813a82ee>](cfq_put_queue+0x7e/0xd0)
> 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> Next obj: start=ffff88001dab3378, len=232
> Redzone: 0xd84156c5635688c0/0xd84156c5635688c0.
> Last user: [<ffffffff813a8e53>](cfq_get_queue+0x153/0x670)
> 000: 02 00 00 00 21 01 00 00 e0 c9 b1 1d 00 88 ff ff ....!...........
> 010: 89 96 ae 18 00 88 ff ff 00 00 00 00 00 00 00 00 ................
>
> The field at 0x70 which is being updated after being freed is
> cfqq->fifo. Interestingly, it didn't lead to any visible failure.

That's pretty odd. Given Hughs report as well, it sure does sound like
we now have some life time issues with cfqq's.

--
Jens Axboe



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