From 903b8a8d4835a796f582033802c83283886f4a3d Mon Sep 17 00:00:00 2001 From: Karsten Wiese Date: Thu, 28 Feb 2008 15:10:50 +0100 Subject: clockevents: optimise tick_nohz_stop_sched_tick() a bit Call ts = &per_cpu(tick_cpu_sched, cpu); and cpu = smp_processor_id(); once instead of twice. No functional change done, as changed code runs with local irq off. Reduces source lines and text size (20bytes on x86_64). [ akpm@linux-foundation.org: Build fix ] Signed-off-by: Karsten Wiese Cc: Andrew Morton Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 686da821d37..69dba0c7172 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -158,9 +158,8 @@ void tick_nohz_stop_idle(int cpu) } } -static ktime_t tick_nohz_start_idle(int cpu) +static ktime_t tick_nohz_start_idle(struct tick_sched *ts) { - struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); ktime_t now, delta; now = ktime_get(); @@ -201,8 +200,8 @@ void tick_nohz_stop_sched_tick(void) local_irq_save(flags); cpu = smp_processor_id(); - now = tick_nohz_start_idle(cpu); ts = &per_cpu(tick_cpu_sched, cpu); + now = tick_nohz_start_idle(ts); /* * If this cpu is offline and it is the one which updates @@ -222,7 +221,6 @@ void tick_nohz_stop_sched_tick(void) if (need_resched()) goto end; - cpu = smp_processor_id(); if (unlikely(local_softirq_pending())) { static int ratelimit; -- cgit v1.2.3 From 6993fc5bbc5d63ccd55985b39c34417e430e75e9 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 30 Jan 2008 13:30:02 +0100 Subject: clocksource: make clocksource watchdog cycle through online CPUs This way it checks if the clocks are synchronized between CPUs too. This might be able to detect slowly drifting TSCs which only go wrong over longer time. Signed-off-by: Andi Kleen Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- kernel/time/clocksource.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 7f60097d443..912156dd600 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -141,8 +141,16 @@ static void clocksource_watchdog(unsigned long data) } if (!list_empty(&watchdog_list)) { - __mod_timer(&watchdog_timer, - watchdog_timer.expires + WATCHDOG_INTERVAL); + /* + * Cycle through CPUs to check if the CPUs stay + * synchronized to each other. + */ + int next_cpu = next_cpu(raw_smp_processor_id(), cpu_online_map); + + if (next_cpu >= NR_CPUS) + next_cpu = first_cpu(cpu_online_map); + watchdog_timer.expires += WATCHDOG_INTERVAL; + add_timer_on(&watchdog_timer, next_cpu); } spin_unlock(&watchdog_lock); } @@ -164,7 +172,8 @@ static void clocksource_check_watchdog(struct clocksource *cs) if (!started && watchdog) { watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; - add_timer(&watchdog_timer); + add_timer_on(&watchdog_timer, + first_cpu(cpu_online_map)); } } else { if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) @@ -185,7 +194,8 @@ static void clocksource_check_watchdog(struct clocksource *cs) watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; - add_timer(&watchdog_timer); + add_timer_on(&watchdog_timer, + first_cpu(cpu_online_map)); } } } -- cgit v1.2.3