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From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>,
	mingo@kernel.org, linux-kernel@vger.kernel.org,
	eranian@gmail.com, mark.rutland@arm.com,
	torvalds@linux-foundation.org, tglx@linutronix.de
Subject: Re: [RFC][PATCH 2/3] perf: Add a bit of paranoia
Date: Wed, 4 Feb 2015 17:33:36 +0100	[thread overview]
Message-ID: <20150204163336.GC5029@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150204145136.GB31111@krava.brq.redhat.com>

On Wed, Feb 04, 2015 at 03:51:36PM +0100, Jiri Olsa wrote:
> On Mon, Feb 02, 2015 at 06:32:32PM +0100, Peter Zijlstra wrote:
> > > That looks like tail recursive fun! An irq work that raises and irq work
> > > ad infinitum. Lemme see if I can squash that.. didn't we have something
> > > like this before... /me goes look.
> > 
> > 
> > Does this make it go away?
> > 
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -4413,6 +4413,8 @@ static void perf_pending_event(struct ir
> >  	struct perf_event *event = container_of(entry,
> >  			struct perf_event, pending);
> >  
> > +	int rctx = perf_swevent_get_recursion_context();
> > +
> 
> hum, you should check the rctx
> 
> 	if (rctx == -1)
> 		return;

D'uh, yes.

> also this recursion is bound to swevent_htable, should we rather add
> separate ctx data for irq_work to limit the clashing with SW events?

No, we explicitly want to disable software events while handling the
irq_work. The problem as reported looks like irq_work triggering a
swevent (tp actually, but that's classed the same) generates a new
irq_work, and we get stuck in an endless cycle of that.

So by effectively disabling swevents while processing the irq_work we
should break the cycle.

  reply	other threads:[~2015-02-04 16:33 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-23 12:51 [RFC][PATCH 0/3] perf fixes Peter Zijlstra
2015-01-23 12:52 ` [RFC][PATCH 1/3] perf: Tighten (and fix) the grouping condition Peter Zijlstra
2015-01-23 15:02   ` Mark Rutland
2015-01-23 15:07     ` Peter Zijlstra
2015-01-23 15:22       ` Mark Rutland
2015-02-04 12:59         ` Peter Zijlstra
2015-01-28 14:30   ` [tip:perf/urgent] " tip-bot for Peter Zijlstra
2015-01-23 12:52 ` [RFC][PATCH 2/3] perf: Add a bit of paranoia Peter Zijlstra
2015-01-26 16:26   ` Peter Zijlstra
2015-01-27 21:28     ` Vince Weaver
2015-01-29  2:16       ` Vince Weaver
2015-01-29  7:51         ` Jiri Olsa
2015-01-29 13:44           ` Peter Zijlstra
2015-02-04 14:39             ` [tip:perf/core] perf: Fix put_event() ctx lock tip-bot for Peter Zijlstra
2015-01-29 14:47     ` [RFC][PATCH 2/3] perf: Add a bit of paranoia Peter Zijlstra
2015-02-02  6:33       ` Vince Weaver
2015-02-02 15:42         ` Peter Zijlstra
2015-02-02 17:32           ` Peter Zijlstra
2015-02-04 14:51             ` Jiri Olsa
2015-02-04 16:33               ` Peter Zijlstra [this message]
2015-02-04 16:43                 ` Peter Zijlstra
2015-02-04 14:39     ` [tip:perf/core] perf: Fix move_group() order tip-bot for Peter Zijlstra (Intel)
2015-02-04 14:39   ` [tip:perf/core] perf: Add a bit of paranoia tip-bot for Peter Zijlstra
2015-01-23 12:52 ` [RFC][PATCH 3/3] perf: Fix event->ctx locking Peter Zijlstra
2015-02-04 14:39   ` [tip:perf/core] " tip-bot for Peter Zijlstra
2015-01-26 14:30 ` [RFC][PATCH 0/3] perf fixes Vince Weaver
2015-01-26 18:03   ` Vince Weaver
2015-01-26 18:34     ` Jiri Olsa
2015-01-26 18:52       ` Vince Weaver

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