From 1f7b7081568bca281f4ef42096206180cfaced00 Mon Sep 17 00:00:00 2001 From: Ladislav Michl Date: Thu, 10 Jan 2019 00:19:44 +0100 Subject: PM-runtime: Fix 'jiffies' in comments after switch to hrtimers PM-runtime now uses the hrtimers infrastructure for autosuspend, however comments still reference 'jiffies'. Fixes: 8234f6734c5d (PM-runtime: Switch autosuspend over to using hrtimers) Signed-off-by: Ladislav Michl Signed-off-by: Rafael J. Wysocki --- drivers/base/power/runtime.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'drivers/base/power/runtime.c') diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 70624695b6d5..a282e74d1a16 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -121,7 +121,7 @@ static void pm_runtime_cancel_pending(struct device *dev) * Compute the autosuspend-delay expiration time based on the device's * power.last_busy time. If the delay has already expired or is disabled * (negative) or the power.use_autosuspend flag isn't set, return 0. - * Otherwise return the expiration time in jiffies (adjusted to be nonzero). + * Otherwise return the expiration time in nanoseconds (adjusted to be nonzero). * * This function may be called either with or without dev->power.lock held. * Either way it can be racy, since power.last_busy may be updated at any time. @@ -905,7 +905,10 @@ static enum hrtimer_restart pm_suspend_timer_fn(struct hrtimer *timer) spin_lock_irqsave(&dev->power.lock, flags); expires = dev->power.timer_expires; - /* If 'expire' is after 'jiffies' we've been called too early. */ + /* + * If 'expires' is after the current time, we've been called + * too early. + */ if (expires > 0 && expires < ktime_to_ns(ktime_get())) { dev->power.timer_expires = 0; rpm_suspend(dev, dev->power.timer_autosuspends ? -- cgit v1.2.3 From ca27e4cd0bdd87e33fda38e6e3d18d36d54356d4 Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Thu, 10 Jan 2019 10:00:40 +0100 Subject: PM-runtime: Fix autosuspend_delay on 32bits arch Cast autosuspend_delay to u64 to make sure that the full computation of 'expires' or slack will be done in u64, even on 32bits arch. Otherwise, any delay greater than 2^31 nsec can overflow if signed 32bits is used when converting delay from msec to nsec. Fixes: 8234f6734c5d (PM-runtime: Switch autosuspend over to using hrtimers) Reported-by: Tony Lindgren Tested-by: Tony Lindgren Signed-off-by: Vincent Guittot Signed-off-by: Rafael J. Wysocki --- drivers/base/power/runtime.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/base/power/runtime.c') diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index a282e74d1a16..457be03b744d 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -141,7 +141,7 @@ u64 pm_runtime_autosuspend_expiration(struct device *dev) last_busy = READ_ONCE(dev->power.last_busy); - expires = last_busy + autosuspend_delay * NSEC_PER_MSEC; + expires = last_busy + (u64)autosuspend_delay * NSEC_PER_MSEC; if (expires <= now) expires = 0; /* Already expired. */ @@ -525,7 +525,7 @@ static int rpm_suspend(struct device *dev, int rpmflags) * We add a slack of 25% to gather wakeups * without sacrificing the granularity. */ - u64 slack = READ_ONCE(dev->power.autosuspend_delay) * + u64 slack = (u64)READ_ONCE(dev->power.autosuspend_delay) * (NSEC_PER_MSEC >> 2); dev->power.timer_expires = expires; -- cgit v1.2.3 From 15efb47dc560849d0c07db96fdad5121f2cf736e Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Wed, 30 Jan 2019 18:26:02 +0100 Subject: PM-runtime: Fix deadlock with ktime_get() A deadlock has been seen when swicthing clocksources which use PM-runtime. The call path is: change_clocksource ... write_seqcount_begin ... timekeeping_update ... sh_cmt_clocksource_enable ... rpm_resume pm_runtime_mark_last_busy ktime_get do read_seqcount_begin while read_seqcount_retry .... write_seqcount_end Although we should be safe because we haven't yet changed the clocksource at that time, we can't do that because of seqcount protection. Use ktime_get_mono_fast_ns() instead which is lock safe for such cases. With ktime_get_mono_fast_ns, the timestamp is not guaranteed to be monotonic across an update and as a result can goes backward. According to update_fast_timekeeper() description: "In the worst case, this can result is a slightly wrong timestamp (a few nanoseconds)". For PM-runtime autosuspend, this means only that the suspend decision may be slightly suboptimal. Fixes: 8234f6734c5d ("PM-runtime: Switch autosuspend over to using hrtimers") Reported-by: Biju Das Signed-off-by: Vincent Guittot Reviewed-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki --- drivers/base/power/runtime.c | 10 +++++----- include/linux/pm_runtime.h | 2 +- 2 files changed, 6 insertions(+), 6 deletions(-) (limited to 'drivers/base/power/runtime.c') diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 457be03b744d..0ea2139c50d8 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -130,7 +130,7 @@ u64 pm_runtime_autosuspend_expiration(struct device *dev) { int autosuspend_delay; u64 last_busy, expires = 0; - u64 now = ktime_to_ns(ktime_get()); + u64 now = ktime_get_mono_fast_ns(); if (!dev->power.use_autosuspend) goto out; @@ -909,7 +909,7 @@ static enum hrtimer_restart pm_suspend_timer_fn(struct hrtimer *timer) * If 'expires' is after the current time, we've been called * too early. */ - if (expires > 0 && expires < ktime_to_ns(ktime_get())) { + if (expires > 0 && expires < ktime_get_mono_fast_ns()) { dev->power.timer_expires = 0; rpm_suspend(dev, dev->power.timer_autosuspends ? (RPM_ASYNC | RPM_AUTO) : RPM_ASYNC); @@ -928,7 +928,7 @@ static enum hrtimer_restart pm_suspend_timer_fn(struct hrtimer *timer) int pm_schedule_suspend(struct device *dev, unsigned int delay) { unsigned long flags; - ktime_t expires; + u64 expires; int retval; spin_lock_irqsave(&dev->power.lock, flags); @@ -945,8 +945,8 @@ int pm_schedule_suspend(struct device *dev, unsigned int delay) /* Other scheduled or pending requests need to be canceled. */ pm_runtime_cancel_pending(dev); - expires = ktime_add(ktime_get(), ms_to_ktime(delay)); - dev->power.timer_expires = ktime_to_ns(expires); + expires = ktime_get_mono_fast_ns() + (u64)delay * NSEC_PER_MSEC; + dev->power.timer_expires = expires; dev->power.timer_autosuspends = 0; hrtimer_start(&dev->power.suspend_timer, expires, HRTIMER_MODE_ABS); diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index 54af4eef169f..fed5be706bc9 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -105,7 +105,7 @@ static inline bool pm_runtime_callbacks_present(struct device *dev) static inline void pm_runtime_mark_last_busy(struct device *dev) { - WRITE_ONCE(dev->power.last_busy, ktime_to_ns(ktime_get())); + WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns()); } static inline bool pm_runtime_is_irq_safe(struct device *dev) -- cgit v1.2.3