path: root/kernel/time/hrtimer.c
diff options
authorAnna-Maria Gleixner <anna-maria@linutronix.de>2017-12-21 11:41:49 +0100
committerIngo Molnar <mingo@kernel.org>2018-01-16 02:53:58 +0100
commit14c803419de6acba08e143d51813ac5e0f3443b8 (patch)
tree3cdb76711c71225d12ac6206f661e6ab32f3b734 /kernel/time/hrtimer.c
parenthrtimer: Unify hrtimer removal handling (diff)
hrtimer: Unify remote enqueue handling
hrtimer_reprogram() is conditionally invoked from hrtimer_start_range_ns() when hrtimer_cpu_base.hres_active is true. In the !hres_active case there is a special condition for the nohz_active case: If the newly enqueued timer expires before the first expiring timer on a remote CPU then the remote CPU needs to be notified and woken up from a NOHZ idle sleep to take the new first expiring timer into account. Previous changes have already established the prerequisites to make the remote enqueue behaviour the same whether high resolution mode is active or not: If the to be enqueued timer expires before the first expiring timer on a remote CPU, then it cannot be enqueued there. This was done for the high resolution mode because there is no way to access the remote CPU timer hardware. The same is true for NOHZ, but was handled differently by unconditionally enqueuing the timer and waking up the remote CPU so it can reprogram its timer. Again there is no compelling reason for this difference. hrtimer_check_target(), which makes the 'can remote enqueue' decision is already unconditional, but not yet functional because nothing updates hrtimer_cpu_base.expires_next in the !hres_active case. To unify this the following changes are required: 1) Make the store of the new first expiry time unconditonal in hrtimer_reprogram() and check __hrtimer_hres_active() before proceeding to the actual hardware access. This check also lets the compiler eliminate the rest of the function in case of CONFIG_HIGH_RES_TIMERS=n. 2) Invoke hrtimer_reprogram() unconditionally from hrtimer_start_range_ns() 3) Remove the remote wakeup special case for the !high_res && nohz_active case. Confine the timers_nohz_active static key to timer.c which is the only user now. Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Christoph Hellwig <hch@lst.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: keescook@chromium.org Link: http://lkml.kernel.org/r/20171221104205.7269-21-anna-maria@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/time/hrtimer.c')
1 files changed, 6 insertions, 12 deletions
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index e6a78ae103ca..1c68bf21f603 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -685,21 +685,24 @@ static void hrtimer_reprogram(struct hrtimer *timer,
/* Update the pointer to the next expiring timer */
cpu_base->next_timer = timer;
+ cpu_base->expires_next = expires;
+ * If hres is not active, hardware does not have to be
+ * programmed yet.
+ *
* If a hang was detected in the last timer interrupt then we
* do not schedule a timer which is earlier than the expiry
* which we enforced in the hang detection. We want the system
* to make progress.
- if (cpu_base->hang_detected)
+ if (!__hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
* Program the timer hardware. We enforce the expiry for
* events which are already in the past.
- cpu_base->expires_next = expires;
tick_program_event(expires, 1);
@@ -936,16 +939,7 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
if (!leftmost)
goto unlock;
- if (!hrtimer_is_hres_active(timer)) {
- /*
- * Kick to reschedule the next tick to handle the new timer
- * on dynticks target.
- */
- if (is_timers_nohz_active())
- wake_up_nohz_cpu(new_base->cpu_base->cpu);
- } else {
- hrtimer_reprogram(timer, new_base);
- }
+ hrtimer_reprogram(timer, new_base);
unlock_hrtimer_base(timer, &flags);