4.4.102-rt117-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Sebastian Andrzej Siewior <[email protected]> We must not wake any process (and thus acquire the pi->lock) while holding the hrtimer's base lock. This does not happen usually because the hrtimer-callback is invoked in IRQ-context and so raise_softirq_irqoff() does not wakeup a process. However during CPU-hotplug it might get called from hrtimers_dead_cpu() which would wakeup the thread immediately. Reported-by: Mike Galbraith <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- kernel/time/hrtimer.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 759913626eec..78066f7ea2a2 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1461,7 +1461,7 @@ static inline int hrtimer_rt_defer(struct hrtimer *timer) { return 0; } static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer); -static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now) +static int __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now) { struct hrtimer_clock_base *base = cpu_base->clock_base; unsigned int active = cpu_base->active_bases; @@ -1511,8 +1511,7 @@ static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now) raise = 1; } } - if (raise) - raise_softirq_irqoff(HRTIMER_SOFTIRQ); + return raise; } #ifdef CONFIG_HIGH_RES_TIMERS @@ -1526,6 +1525,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases); ktime_t expires_next, now, entry_time, delta; int retries = 0; + int raise; BUG_ON(!cpu_base->hres_active); cpu_base->nr_events++; @@ -1544,7 +1544,7 @@ retry: */ cpu_base->expires_next.tv64 = KTIME_MAX; - __hrtimer_run_queues(cpu_base, now); + raise = __hrtimer_run_queues(cpu_base, now); /* Reevaluate the clock bases for the next expiry */ expires_next = __hrtimer_get_next_event(cpu_base); @@ -1555,6 +1555,8 @@ retry: cpu_base->expires_next = expires_next; cpu_base->in_hrtirq = 0; raw_spin_unlock(&cpu_base->lock); + if (raise) + raise_softirq_irqoff(HRTIMER_SOFTIRQ); /* Reprogramming necessary ? */ if (!tick_program_event(expires_next, 0)) { @@ -1634,6 +1636,7 @@ void hrtimer_run_queues(void) { struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases); ktime_t now; + int raise; if (__hrtimer_hres_active(cpu_base)) return; @@ -1652,8 +1655,10 @@ void hrtimer_run_queues(void) raw_spin_lock(&cpu_base->lock); now = hrtimer_update_base(cpu_base); - __hrtimer_run_queues(cpu_base, now); + raise = __hrtimer_run_queues(cpu_base, now); raw_spin_unlock(&cpu_base->lock); + if (raise) + raise_softirq_irqoff(HRTIMER_SOFTIRQ); } /* -- 2.13.2
