From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755202AbcFHNMm (ORCPT ); Wed, 8 Jun 2016 09:12:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59620 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754724AbcFHNMk (ORCPT ); Wed, 8 Jun 2016 09:12:40 -0400 Date: Wed, 8 Jun 2016 08:12:37 -0500 From: Josh Poimboeuf To: Ingo Molnar Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, Mel Gorman , Matt Fleming , Srikar Dronamraju Subject: Re: [PATCH 2/2] sched/debug: fix deadlock when enabling sched events Message-ID: <20160608131237.3tixvrtpqvfv5kmg@treble> References: <50a0f7f2a5f8d69e0440c3430f06be7ccbe59903.1465322027.git.jpoimboe@redhat.com> <20160608075612.GA9369@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160608075612.GA9369@gmail.com> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 08 Jun 2016 13:12:39 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 08, 2016 at 09:56:12AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf wrote: > > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -789,6 +789,13 @@ static void update_curr_fair(struct rq *rq) > > update_curr(cfs_rq_of(&rq->curr->se)); > > } > > > > +void trace_sched_stat_register(void) > > +{ > > +#ifdef CONFIG_SCHEDSTATS > > + force_schedstat_enabled(); > > +#endif > > +} > > I think it would be cleaner to provide an empty force_schedstat_enabled() > definition in sched.h, on !CONFIG_SCHEDSTATS. Yes, agreed. > But it might make sense to further decouple schedstats from tracing? Looking at how we could do that: - The sched_stat_wait tracepoint is dependent on the wait_start schedstat. - The sched_stat_sleep tracepoint is dependent on the sleep_start schedstat. - The sched_stat_iowait and sched_stat_blocked tracepoints are dependent on the block_start schedstat. We could move those three schedstats values out of sched_statistics and into sched_entity, and then always update them regardless of CONFIG_SCHEDSTATS. That would ensure these tracepoints always work. But then again it would add a little bit of runtime overhead. I don't have a strong opinion either way. Thoughts? -- Josh