From: Sebastian Andrzej Siewior Date: Tue, 27 Jun 2017 16:15:38 +0000 (+0200) Subject: timers: Make the cpu base lock raw X-Git-Tag: v4.14-rc1~630^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2287d8664fe7345ead891017eccd879fc605305e;p=platform%2Fkernel%2Flinux-rpi.git timers: Make the cpu base lock raw The timers cpu base lock could not be converted to a raw spinlock becaue the lock held time was non-deterministic due to cascading and long lasting timer wheel traversals. The rework of the timer wheel to the new non-cascading model removed also the wheel traversals and the lock held times are deterministic now. This allows to make the lock raw and thereby unbreaks NOHz* on preempt-RT. Signed-off-by: Sebastian Andrzej Siewior Link: http://lkml.kernel.org/r/20170627161538.30257-1-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner --- diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 709a404..71ce3f4 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -195,7 +195,7 @@ EXPORT_SYMBOL(jiffies_64); #endif struct timer_base { - spinlock_t lock; + raw_spinlock_t lock; struct timer_list *running_timer; unsigned long clk; unsigned long next_expiry; @@ -913,10 +913,10 @@ static struct timer_base *lock_timer_base(struct timer_list *timer, if (!(tf & TIMER_MIGRATING)) { base = get_timer_base(tf); - spin_lock_irqsave(&base->lock, *flags); + raw_spin_lock_irqsave(&base->lock, *flags); if (timer->flags == tf) return base; - spin_unlock_irqrestore(&base->lock, *flags); + raw_spin_unlock_irqrestore(&base->lock, *flags); } cpu_relax(); } @@ -986,9 +986,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only) /* See the comment in lock_timer_base() */ timer->flags |= TIMER_MIGRATING; - spin_unlock(&base->lock); + raw_spin_unlock(&base->lock); base = new_base; - spin_lock(&base->lock); + raw_spin_lock(&base->lock); WRITE_ONCE(timer->flags, (timer->flags & ~TIMER_BASEMASK) | base->cpu); } @@ -1013,7 +1013,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only) } out_unlock: - spin_unlock_irqrestore(&base->lock, flags); + raw_spin_unlock_irqrestore(&base->lock, flags); return ret; } @@ -1106,16 +1106,16 @@ void add_timer_on(struct timer_list *timer, int cpu) if (base != new_base) { timer->flags |= TIMER_MIGRATING; - spin_unlock(&base->lock); + raw_spin_unlock(&base->lock); base = new_base; - spin_lock(&base->lock); + raw_spin_lock(&base->lock); WRITE_ONCE(timer->flags, (timer->flags & ~TIMER_BASEMASK) | cpu); } debug_activate(timer, timer->expires); internal_add_timer(base, timer); - spin_unlock_irqrestore(&base->lock, flags); + raw_spin_unlock_irqrestore(&base->lock, flags); } EXPORT_SYMBOL_GPL(add_timer_on); @@ -1141,7 +1141,7 @@ int del_timer(struct timer_list *timer) if (timer_pending(timer)) { base = lock_timer_base(timer, &flags); ret = detach_if_pending(timer, base, true); - spin_unlock_irqrestore(&base->lock, flags); + raw_spin_unlock_irqrestore(&base->lock, flags); } return ret; @@ -1168,7 +1168,7 @@ int try_to_del_timer_sync(struct timer_list *timer) if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); - spin_unlock_irqrestore(&base->lock, flags); + raw_spin_unlock_irqrestore(&base->lock, flags); return ret; } @@ -1299,13 +1299,13 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head) data = timer->data; if (timer->flags & TIMER_IRQSAFE) { - spin_unlock(&base->lock); + raw_spin_unlock(&base->lock); call_timer_fn(timer, fn, data); - spin_lock(&base->lock); + raw_spin_lock(&base->lock); } else { - spin_unlock_irq(&base->lock); + raw_spin_unlock_irq(&base->lock); call_timer_fn(timer, fn, data); - spin_lock_irq(&base->lock); + raw_spin_lock_irq(&base->lock); } } } @@ -1474,7 +1474,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) if (cpu_is_offline(smp_processor_id())) return expires; - spin_lock(&base->lock); + raw_spin_lock(&base->lock); nextevt = __next_timer_interrupt(base); is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA); base->next_expiry = nextevt; @@ -1502,7 +1502,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) if ((expires - basem) > TICK_NSEC) base->is_idle = true; } - spin_unlock(&base->lock); + raw_spin_unlock(&base->lock); return cmp_next_hrtimer_event(basem, expires); } @@ -1590,7 +1590,7 @@ static inline void __run_timers(struct timer_base *base) if (!time_after_eq(jiffies, base->clk)) return; - spin_lock_irq(&base->lock); + raw_spin_lock_irq(&base->lock); while (time_after_eq(jiffies, base->clk)) { @@ -1601,7 +1601,7 @@ static inline void __run_timers(struct timer_base *base) expire_timers(base, heads + levels); } base->running_timer = NULL; - spin_unlock_irq(&base->lock); + raw_spin_unlock_irq(&base->lock); } /* @@ -1786,16 +1786,16 @@ int timers_dead_cpu(unsigned int cpu) * The caller is globally serialized and nobody else * takes two locks at once, deadlock is not possible. */ - spin_lock_irq(&new_base->lock); - spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING); + raw_spin_lock_irq(&new_base->lock); + raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING); BUG_ON(old_base->running_timer); for (i = 0; i < WHEEL_SIZE; i++) migrate_timer_list(new_base, old_base->vectors + i); - spin_unlock(&old_base->lock); - spin_unlock_irq(&new_base->lock); + raw_spin_unlock(&old_base->lock); + raw_spin_unlock_irq(&new_base->lock); put_cpu_ptr(&timer_bases); } return 0; @@ -1811,7 +1811,7 @@ static void __init init_timer_cpu(int cpu) for (i = 0; i < NR_BASES; i++) { base = per_cpu_ptr(&timer_bases[i], cpu); base->cpu = cpu; - spin_lock_init(&base->lock); + raw_spin_lock_init(&base->lock); base->clk = jiffies; } }