From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Jiri Pirko <jiri@resnulli.us>
Cc: Tejun Heo <tj@kernel.org>,
Joe Lawrence <joe.lawrence@stratus.com>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2 1/2] workqueue: add quiescent state between work items
Date: Tue, 7 Oct 2014 06:43:29 -0700 [thread overview]
Message-ID: <20141007134329.GA4880@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141007072942.GA2088@nanopsycho.orion>
On Tue, Oct 07, 2014 at 09:29:42AM +0200, Jiri Pirko wrote:
> Mon, Oct 06, 2014 at 06:21:58AM CEST, paulmck@linux.vnet.ibm.com wrote:
> >On Sun, Oct 05, 2014 at 03:47:48PM -0400, Tejun Heo wrote:
> >> On Sun, Oct 05, 2014 at 03:21:19PM -0400, Tejun Heo wrote:
> >> > On Sun, Oct 05, 2014 at 01:24:21PM -0400, Joe Lawrence wrote:
> >> > > Similar to the stop_machine deadlock scenario on !PREEMPT kernels
> >> > > addressed in b22ce2785d97 "workqueue: cond_resched() after processing
> >> > > each work item", kworker threads requeueing back-to-back with zero jiffy
> >> > > delay can stall RCU. The cond_resched call introduced in that fix will
> >> > > yield only iff there are other higher priority tasks to run, so force a
> >> > > quiescent RCU state between work items.
> >> > >
> >> > > Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
> >> > > Link: https://lkml.kernel.org/r/20140926105227.01325697@jlaw-desktop.mno.stratus.com
> >> > > Link: https://lkml.kernel.org/r/20140929115445.40221d8e@jlaw-desktop.mno.stratus.com
> >> > > Fixes: b22ce2785d97 ("workqueue: cond_resched() after processing each work item")
> >> > > Cc: <stable@vger.kernel.org>
> >> >
> >> > Applied to wq/for-3.17-fixes. If 3.17 comes out before this gets
> >> > merged, I'll send it as for-3.18.
> >>
> >> Oops, the rcu calls aren't in mainline yet. I think it'd be best to
> >> route these through the RCU tree. Paul, can you please route these
> >> two patches?
> >>
> >> Acked-by: Tejun Heo <tj@kernel.org>
> >
> >Will do!
> >
> >I will try 3.17, failing that, 3.18.
>
>
> Paul, Tehun, how do you propose to fix this on older kernels which do
> not have rcu_note_voluntary_context_switch? I'm particullary interested
> in 3.10.
Hello, Jiri,
Older kernels can instead use rcu_note_context_switch().
Thanx, Paul
next prev parent reply other threads:[~2014-10-07 13:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-05 17:24 [PATCH v2 0/2] workqueue: add RCU quiescent state between items Joe Lawrence
2014-10-05 17:24 ` [PATCH v2 1/2] workqueue: add quiescent state between work items Joe Lawrence
2014-10-05 19:21 ` Tejun Heo
2014-10-05 19:47 ` Tejun Heo
2014-10-06 4:21 ` Paul E. McKenney
2014-10-07 7:29 ` Jiri Pirko
2014-10-07 13:43 ` Paul E. McKenney [this message]
2014-10-07 17:45 ` Joe Lawrence
2014-10-08 3:24 ` Paul E. McKenney
2014-10-08 11:54 ` Jiri Pirko
2014-10-08 12:19 ` Paul E. McKenney
2014-10-05 17:24 ` [PATCH v2 2/2] workqueue: use cond_resched_rcu_qs macro Joe Lawrence
2014-10-05 18:47 ` Paul E. McKenney
2014-10-05 19:48 ` Tejun Heo
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