Messages in this thread | | | Date | Wed, 19 Mar 2014 15:43:39 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH] cifs: Fix possible deadlock with cifs and work queues |
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On Wed, 19 Mar 2014 20:34:07 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 19, 2014 at 03:12:52PM -0400, Steven Rostedt wrote: > > My question to Tejun is, if we create another workqueue, to add the > > rdata->work to, would that prevent the above problem? Or what other > > fixes can we do? > > The way I understand workqueues is that we cannot guarantee concurrency > like this. It tries, but there's no guarantee. > > WQ_MAX_ACTIVE seems to be a hard upper limit of concurrent workers. So > given 511 other blocked works, the described problem will always happen. > > Creating another workqueue doesn't actually create more threads.
But I noticed this:
Before patch:
# ps aux |grep cifs root 3119 0.0 0.0 0 0 ? S< 14:17 0:00 [cifsiod]
After patch:
# ps aux |grep cifs root 1109 0.0 0.0 0 0 ? S< 15:11 0:00 [cifsiod] root 1111 0.0 0.0 0 0 ? S< 15:11 0:00 [cifsiord]
It looks to me that it does create new threads.
-- Steve
> > There is the kthread_work stuff for if you want a guaranteed worker > thread.
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