From patchwork Thu May 28 13:20:23 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Mundt X-Patchwork-Id: 26743 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n4SDLoWW014928 for ; Thu, 28 May 2009 13:21:51 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761809AbZE1NUm (ORCPT ); Thu, 28 May 2009 09:20:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759872AbZE1NUm (ORCPT ); Thu, 28 May 2009 09:20:42 -0400 Received: from 124x34x33x190.ap124.ftth.ucom.ne.jp ([124.34.33.190]:53231 "EHLO master.linux-sh.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761574AbZE1NUk (ORCPT ); Thu, 28 May 2009 09:20:40 -0400 Received: from localhost (unknown [127.0.0.1]) by master.linux-sh.org (Postfix) with ESMTP id 13A896375A; Thu, 28 May 2009 13:20:24 +0000 (UTC) X-Virus-Scanned: amavisd-new at linux-sh.org Received: from master.linux-sh.org ([127.0.0.1]) by localhost (master.linux-sh.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Yk7ykho+1+AM; Thu, 28 May 2009 22:20:23 +0900 (JST) Received: by master.linux-sh.org (Postfix, from userid 500) id 5CCC66375B; Thu, 28 May 2009 22:20:23 +0900 (JST) Date: Thu, 28 May 2009 22:20:23 +0900 From: Paul Mundt To: Peter Zijlstra Cc: Thomas Gleixner , Daniel Walker , Linus Walleij , Ingo Molnar , Andrew Victor , Haavard Skinnemoen , Andrew Morton , linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, linux-arm-kernel@lists.arm.linux.org.uk, John Stultz Subject: Re: [PATCH] sched: Support current clocksource handling in fallback sched_clock(). Message-ID: <20090528132023.GA29364@linux-sh.org> Mail-Followup-To: Paul Mundt , Peter Zijlstra , Thomas Gleixner , Daniel Walker , Linus Walleij , Ingo Molnar , Andrew Victor , Haavard Skinnemoen , Andrew Morton , linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, linux-arm-kernel@lists.arm.linux.org.uk, John Stultz References: <20090526230855.GA27218@linux-sh.org> <20090527001543.GA8493@linux-sh.org> <1243441525.28705.19.camel@desktop> <20090528091936.GA27545@linux-sh.org> <1243503281.23657.80.camel@twins> <20090528110902.GA27884@linux-sh.org> <20090528124207.GA28830@linux-sh.org> <1243515570.6600.96.camel@laptop> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1243515570.6600.96.camel@laptop> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On Thu, May 28, 2009 at 02:59:30PM +0200, Peter Zijlstra wrote: > On Thu, 2009-05-28 at 21:42 +0900, Paul Mundt wrote: > > > unsigned long long __attribute__((weak)) sched_clock(void) > > { > > - return (unsigned long long)(jiffies - INITIAL_JIFFIES) > > - * (NSEC_PER_SEC / HZ); > > + struct clocksource *clock = ACCESS_ONCE(sched_clocksource); > > + > > + return cyc2ns(clock, clocksource_read(clock)); > > } > > > > > @@ -440,7 +444,17 @@ void clocksource_unregister(struct clocksource *cs) > > list_del(&cs->list); > > if (clocksource_override == cs) > > clocksource_override = NULL; > > + > > next_clocksource = select_clocksource(); > > + > > + /* > > + * If select_clocksource() fails to find another suitable > > + * clocksource for sched_clocksource and we are unregistering > > + * it, switch back to jiffies. > > + */ > > + if (sched_clocksource == cs) > > + sched_clocksource = &clocksource_jiffies; > > + > > spin_unlock_irqrestore(&clocksource_lock, flags); > > } > > > CPU0 CPU1 > > clock = ACCESS_ONCE(sched_clocksource); > > unload module > clocksource_unregister() > sched_clocksource = jiffies > unmap data/text > > cyc2ns(clock, clocksource_read(clock)) <--- fireworks > Right, lets try that again.. --- include/linux/clocksource.h | 4 +++- kernel/sched_clock.c | 13 +++++++++++-- kernel/time/clocksource.c | 19 +++++++++++++++++++ kernel/time/jiffies.c | 2 +- 4 files changed, 34 insertions(+), 4 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index c56457c..2109940 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -202,7 +202,8 @@ struct clocksource { #endif }; -extern struct clocksource *clock; /* current clocksource */ +extern struct clocksource *clock; /* current clocksource */ +extern struct clocksource *sched_clocksource; /* sched_clock() clocksource */ /* * Clock source flags bits:: @@ -212,6 +213,7 @@ extern struct clocksource *clock; /* current clocksource */ #define CLOCK_SOURCE_WATCHDOG 0x10 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 +#define CLOCK_SOURCE_USE_FOR_SCHED_CLOCK 0x40 /* simplify initialization of mask field */ #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index e1d16c9..b51d48d 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -30,6 +30,8 @@ #include #include #include +#include +#include /* * Scheduler clock - returns current time in nanosec units. @@ -38,8 +40,15 @@ */ unsigned long long __attribute__((weak)) sched_clock(void) { - return (unsigned long long)(jiffies - INITIAL_JIFFIES) - * (NSEC_PER_SEC / HZ); + unsigned long long time; + struct clocksource *clock; + + rcu_read_lock(); + clock = rcu_dereference(sched_clocksource); + time = cyc2ns(clock, clocksource_read(clock)); + rcu_read_unlock(); + + return time; } static __read_mostly int sched_clock_running; diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 80189f6..3795954 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -25,6 +25,7 @@ */ #include +#include #include #include #include @@ -109,6 +110,7 @@ EXPORT_SYMBOL(timecounter_cyc2time); /* XXX - Would like a better way for initializing curr_clocksource */ extern struct clocksource clocksource_jiffies; +struct clocksource *sched_clocksource = &clocksource_jiffies; /*[Clocksource internal variables]--------- * curr_clocksource: @@ -362,6 +364,9 @@ static struct clocksource *select_clocksource(void) if (next == curr_clocksource) return NULL; + if (next->flags & CLOCK_SOURCE_USE_FOR_SCHED_CLOCK) + sched_clocksource = next; + return next; } @@ -440,7 +445,21 @@ void clocksource_unregister(struct clocksource *cs) list_del(&cs->list); if (clocksource_override == cs) clocksource_override = NULL; + next_clocksource = select_clocksource(); + + /* + * If select_clocksource() fails to find another suitable + * clocksource for sched_clocksource and we are unregistering + * it, switch back to jiffies. + */ + if (sched_clocksource == cs) { + rcu_assign_pointer(sched_clocksource, &clocksource_jiffies); + spin_unlock_irqrestore(&clocksource_lock, flags); + synchronize_rcu(); + return; + } + spin_unlock_irqrestore(&clocksource_lock, flags); } diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index c3f6c30..727d881 100644 --- a/kernel/time/jiffies.c +++ b/kernel/time/jiffies.c @@ -52,7 +52,7 @@ static cycle_t jiffies_read(struct clocksource *cs) { - return (cycle_t) jiffies; + return (cycle_t) (jiffies - INITIAL_JIFFIES); } struct clocksource clocksource_jiffies = {