From 07a9a7eae86abb796468b225586086d7c4cb59fc Mon Sep 17 00:00:00 2001 From: Anna-Maria Gleixner Date: Thu, 21 Dec 2017 11:41:44 +0100 Subject: hrtimer: Make the remote enqueue check unconditional hrtimer_cpu_base.expires_next is used to cache the next event armed in the timer hardware. The value is used to check whether an hrtimer can be enqueued remotely. If the new hrtimer is expiring before expires_next, then remote enqueue is not possible as the remote hrtimer hardware cannot be accessed for reprogramming to an earlier expiry time. The remote enqueue check is currently conditional on CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active. There is no compelling reason to make this conditional. Move hrtimer_cpu_base.expires_next out of the CONFIG_HIGH_RES_TIMERS=y guarded area and remove the conditionals in hrtimer_check_target(). The check is currently a NOOP for the CONFIG_HIGH_RES_TIMERS=n and the !hrtimer_cpu_base.hres_active case because in these cases nothing updates hrtimer_cpu_base.expires_next yet. This will be changed with later patches which further reduce the #ifdef zoo in this code. Signed-off-by: Anna-Maria Gleixner Cc: Christoph Hellwig Cc: John Stultz Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: keescook@chromium.org Link: http://lkml.kernel.org/r/20171221104205.7269-16-anna-maria@linutronix.de Signed-off-by: Ingo Molnar --- kernel/time/hrtimer.c | 26 ++++++-------------------- 1 file changed, 6 insertions(+), 20 deletions(-) (limited to 'kernel') diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 5a624f9c8408..a9ab67f3e5d5 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -154,26 +154,21 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer, } /* - * With HIGHRES=y we do not migrate the timer when it is expiring - * before the next event on the target cpu because we cannot reprogram - * the target cpu hardware and we would cause it to fire late. + * We do not migrate the timer when it is expiring before the next + * event on the target cpu. When high resolution is enabled, we cannot + * reprogram the target cpu hardware and we would cause it to fire + * late. To keep it simple, we handle the high resolution enabled and + * disabled case similar. * * Called with cpu_base->lock of target cpu held. */ static int hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base) { -#ifdef CONFIG_HIGH_RES_TIMERS ktime_t expires; - if (!new_base->cpu_base->hres_active) - return 0; - expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset); return expires <= new_base->cpu_base->expires_next; -#else - return 0; -#endif } static inline @@ -656,14 +651,6 @@ static void hrtimer_reprogram(struct hrtimer *timer, tick_program_event(expires, 1); } -/* - * Initialize the high resolution related parts of cpu_base - */ -static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) -{ - base->expires_next = KTIME_MAX; -} - /* * Retrigger next event is called after clock was set * @@ -729,7 +716,6 @@ static inline int hrtimer_reprogram(struct hrtimer *timer, { return 0; } -static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { } static inline void retrigger_next_event(void *arg) { } #endif /* CONFIG_HIGH_RES_TIMERS */ @@ -1599,7 +1585,7 @@ int hrtimers_prepare_cpu(unsigned int cpu) cpu_base->cpu = cpu; cpu_base->hres_active = 0; - hrtimer_init_hres(cpu_base); + cpu_base->expires_next = KTIME_MAX; return 0; } -- cgit v1.2.3-70-g09d2