From b845b517b5e3706a3729f6ea83b88ab85f0725b0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 8 Aug 2008 21:47:09 +0200 Subject: printk: robustify printk Avoid deadlocks against rq->lock and xtime_lock by deferring the klogd wakeup by polling from the timer tick. Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/time/tick-sched.c') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 825b4c00fe4..c13d4f18237 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -255,7 +255,7 @@ void tick_nohz_stop_sched_tick(int inidle) next_jiffies = get_next_timer_interrupt(last_jiffies); delta_jiffies = next_jiffies - last_jiffies; - if (rcu_needs_cpu(cpu)) + if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu)) delta_jiffies = 1; /* * Do not stop the tick, if we are only one off -- cgit v1.2.3 From 6441402b1f173fa38e561d3cee7c01c32e5281ad Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 22 Sep 2008 18:46:37 +0200 Subject: clockevents: prevent cpu online to interfere with nohz Impact: rare hang which can be triggered on CPU online. tick_do_timer_cpu keeps track of the CPU which updates jiffies via do_timer. The value -1 is used to signal, that currently no CPU is doing this. There are two cases, where the variable can have this state: boot: necessary for systems where the boot cpu id can be != 0 nohz long idle sleep: When the CPU which did the jiffies update last goes into a long idle sleep it drops the update jiffies duty so another CPU which is not idle can pick it up and keep jiffies going. Using the same value for both situations is wrong, as the CPU online code can see the -1 state when the timer of the newly onlined CPU is setup. The setup for a newly onlined CPU goes through periodic mode and can pick up the do_timer duty without being aware of the nohz / highres mode of the already running system. Use two separate states and make them constants to avoid magic numbers confusion. Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel/time/tick-sched.c') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index a87b0468568..31a14e8caac 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -221,7 +221,7 @@ void tick_nohz_stop_sched_tick(int inidle) */ if (unlikely(!cpu_online(cpu))) { if (cpu == tick_do_timer_cpu) - tick_do_timer_cpu = -1; + tick_do_timer_cpu = TICK_DO_TIMER_NONE; } if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) @@ -303,7 +303,7 @@ void tick_nohz_stop_sched_tick(int inidle) * invoked. */ if (cpu == tick_do_timer_cpu) - tick_do_timer_cpu = -1; + tick_do_timer_cpu = TICK_DO_TIMER_NONE; ts->idle_sleeps++; @@ -468,7 +468,7 @@ static void tick_nohz_handler(struct clock_event_device *dev) * this duty, then the jiffies update is still serialized by * xtime_lock. */ - if (unlikely(tick_do_timer_cpu == -1)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) tick_do_timer_cpu = cpu; /* Check, if the jiffies need an update */ @@ -570,7 +570,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) * this duty, then the jiffies update is still serialized by * xtime_lock. */ - if (unlikely(tick_do_timer_cpu == -1)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) tick_do_timer_cpu = cpu; #endif -- cgit v1.2.3 From 49d670fb8dd62d3ed4e3ed2513538ea65b051aed Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 22 Sep 2008 18:56:01 +0200 Subject: clockevents: prevent stale tick_next_period for onlining CPUs Impact: possible hang on CPU onlining in timer one shot mode. The tick_next_period variable is only used during boot on nohz/highres enabled systems, but for CPU onlining it needs to be maintained when the per cpu clock events device operates in one shot mode. Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'kernel/time/tick-sched.c') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 31a14e8caac..39019b3f762 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -75,6 +75,9 @@ static void tick_do_update_jiffies64(ktime_t now) incr * ticks); } do_timer(++ticks); + + /* Keep the tick_next_period variable up to date */ + tick_next_period = ktime_add(last_jiffies_update, tick_period); } write_sequnlock(&xtime_lock); } -- cgit v1.2.3 From ccc7dadf736639da86f3e0c86832c11a66fc8221 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 29 Sep 2008 15:47:42 +0200 Subject: hrtimer: prevent migration of per CPU hrtimers Impact: per CPU hrtimers can be migrated from a dead CPU The hrtimer code has no knowledge about per CPU timers, but we need to prevent the migration of such timers and warn when such a timer is active at migration time. Explicitely mark the timers as per CPU and use a more understandable mode descriptor for the interrupts safe unlocked callback mode, which is used by hrtimer_sleeper and the scheduler code. Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/time/tick-sched.c') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 39019b3f762..cb02324bdb8 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -625,7 +625,7 @@ void tick_setup_sched_timer(void) */ hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); ts->sched_timer.function = tick_sched_timer; - ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ; + ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_PERCPU; /* Get the next period (per cpu) */ ts->sched_timer.expires = tick_init_jiffy_update(); -- cgit v1.2.3 From 8083e4ad970e4eb567e31037060cdd4ba346f0c0 Mon Sep 17 00:00:00 2001 From: "venkatesh.pallipadi@intel.com" Date: Mon, 4 Aug 2008 11:59:11 -0700 Subject: [CPUFREQ][5/6] cpufreq: Changes to get_cpu_idle_time_us(), used by ondemand governor export get_cpu_idle_time_us() for it to be used in ondemand governor. Last update time can be current time when the CPU is currently non-idle, accounting for the busy time since last idle. Signed-off-by: Venkatesh Pallipadi Signed-off-by: Dave Jones --- kernel/time/tick-sched.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'kernel/time/tick-sched.c') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index cb02324bdb8..a4d21939816 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -20,6 +20,7 @@ #include #include #include +#include #include @@ -190,9 +191,17 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) { struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); - *last_update_time = ktime_to_us(ts->idle_lastupdate); + if (!tick_nohz_enabled) + return -1; + + if (ts->idle_active) + *last_update_time = ktime_to_us(ts->idle_lastupdate); + else + *last_update_time = ktime_to_us(ktime_get()); + return ktime_to_us(ts->idle_sleeptime); } +EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); /** * tick_nohz_stop_sched_tick - stop the idle tick from the idle task -- cgit v1.2.3