Messages in this thread |  | | Subject | Re: [PATCH] blk-mq: Directly schedule q->timeout_work when aborting a request | From | Jens Axboe <> | Date | Mon, 2 Apr 2018 16:35:58 -0600 |
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On 4/2/18 4:04 PM, Tejun Heo wrote: > Request abortion is performed by overriding deadline to now and > scheduling timeout handling immediately. For the latter part, the > code was using mod_timer(timeout, 0) which can't guarantee that the > timer runs afterwards. Let's schedule the underlying work item > directly instead. > > This fixes the hangs during probing reported by Sitsofe but it isn't > yet clear to me how the failure can happen reliably if it's just the > above described race condition. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Reported-by: Sitsofe Wheeler <sitsofe@gmail.com> > Reported-by: Meelis Roos <mroos@linux.ee> > Fixes: 358f70da49d7 ("blk-mq: make blk_abort_request() trigger timeout path") > Cc: stable@vger.kernel.org # v4.16 > Link: http://lkml.kernel.org/r/CALjAwxh-PVYFnYFCJpGOja+m5SzZ8Sa4J7ohxdK=r8NyOF-EMA@mail.gmail.com > Link: http://lkml.kernel.org/r/alpine.LRH.2.21.1802261049140.4893@math.ut.ee > --- > Hello, > > I don't have the full explanation yet but here's a preliminary patch. > > Thanks. > > block/blk-timeout.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/blk-timeout.c b/block/blk-timeout.c > index a05e367..f0e6e41 100644 > --- a/block/blk-timeout.c > +++ b/block/blk-timeout.c > @@ -165,7 +165,7 @@ void blk_abort_request(struct request *req) > * No need for fancy synchronizations. > */ > blk_rq_set_deadline(req, jiffies); > - mod_timer(&req->q->timeout, 0); > + kblockd_schedule_work(&req->q->timeout_work); > } else { > if (blk_mark_rq_complete(req)) > return;
In any case, it's cleaner than relying on mod_timer(.., 0). If that doesn't guarantee that the timer runs again, I can see how a race with the running timer could prevent us from seeing the timeout after an abort.
I'll apply this, thanks.
-- Jens Axboe
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