Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753836Ab3FDM1T (ORCPT ); Tue, 4 Jun 2013 08:27:19 -0400 Received: from mail-ea0-f181.google.com ([209.85.215.181]:42976 "EHLO mail-ea0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753169Ab3FDM1R (ORCPT ); Tue, 4 Jun 2013 08:27:17 -0400 Date: Tue, 4 Jun 2013 14:27:13 +0200 From: Frederic Weisbecker To: Steven Rostedt Cc: Peter Zijlstra , LKML , "Paul E. McKenney" , Dave Jones , Ingo Molnar Subject: Re: [PATCH v2][RFC] tracing/context-tracking: Add preempt_schedule_context() for tracing Message-ID: <20130604122712.GE14973@somewhere> References: <1369943981.26799.43.camel@gandalf.local.home> <20130531134319.GE5932@somewhere> <1370013528.26799.49.camel@gandalf.local.home> <20130531160101.GB5910@twins.programming.kicks-ass.net> <1370050218.26799.87.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1370050218.26799.87.camel@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2044 Lines: 63 On Fri, May 31, 2013 at 09:30:18PM -0400, Steven Rostedt wrote: > diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c > index 65349f0..15c9f2e 100644 > --- a/kernel/context_tracking.c > +++ b/kernel/context_tracking.c > @@ -71,6 +71,44 @@ void user_enter(void) > local_irq_restore(flags); > } > > +/** > + * preempt_schedule_context - preempt_schedule called by tracing > + * > + * The tracing infrastructure uses preempt_enable_notrace to prevent > + * recursion and tracing preempt enabling caused by the tracing > + * infrastructure itself. But as tracing can happen in areas coming > + * from userspace or just about to enter userspace, a preempt enable > + * can occur before user_exit() is called. This will cause the scheduler > + * to be called when the system is still in usermode. > + * > + * To prevent this, the preempt_enable_notrace will use this function > + * instead of preempt_schedule() to exit user context if needed before > + * calling the scheduler. > + */ > +void __sched notrace preempt_schedule_context(void) Should it be under CONFIG_PREEMPT? > +{ > + struct thread_info *ti = current_thread_info(); > + enum ctx_state prev_ctx; > + > + if (likely(ti->preempt_count || irqs_disabled())) > + return; > + > + /* > + * Need to disable preemption in case user_exit() is traced > + * and the tracer calls preempt_enable_notrace() causing > + * an infinite recursion. > + */ > + preempt_disable_notrace(); > + prev_ctx = exception_enter(); > + preempt_enable_no_resched_notrace(); > + > + preempt_schedule(); > + > + preempt_disable_notrace(); > + exception_exit(prev_ctx); > + preempt_enable_notrace(); > +} > +EXPORT_SYMBOL(preempt_schedule_context); > > /** > * user_exit - Inform the context tracking that the CPU is > -- > 1.7.3.4 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/