Re: [PATCH 1/2] blk-mq: don't complete un-started request in timeout handler

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, 2017-03-15 at 20:40 +0800, Ming Lei wrote:
> On Wed, Mar 15, 2017 at 08:18:53PM +0800, Ming Lei wrote:
> > On Wed, Mar 15, 2017 at 12:07:37AM +0000, Bart Van Assche wrote:
> > 
> > > or __blk_mq_requeue_request(). Another issue with this function is that the
> > 
> > __blk_mq_requeue_request() can be run from two pathes:
> > 
> > 	- dispatch failure, in which case the req/tag isn't released to tag set
> > 	
> > 	- IO completion path, in which COMPLETE flag is cleared before requeue.
> > 	
> > so I can't see races with timeout in case of start rq vs. requeue rq. 
> 
> Actually rq/tag won't be released to tag set if it will be requeued, so
> the timeout race is nothing to do with requeue.

Hello Ming,

Please have another look at __blk_mq_requeue_request(). In that function
the following code occurs: if (test_and_clear_bit(REQ_ATOM_STARTED,
&rq->atomic_flags)) { ... }

I think the REQ_ATOM_STARTED check in blk_mq_check_expired() races with the
test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags) call in
__blk_mq_requeue_request().

Bart.



[Index of Archives]     [Linux RAID]     [Linux SCSI]     [Linux ATA RAID]     [IDE]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Device Mapper]

  Powered by Linux