Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (5021b918) · Commits · 戴 / test

kernel/time/tick-broadcast-hrtimer.c

+29 −33

Original line number	Diff line number	Diff line
		@@ -42,39 +42,39 @@ static int bc_shutdown(struct clock_event_device *evt)
		*/
		static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
		{
		int bc_moved;
		/*
		* We try to cancel the timer first. If the callback is on
		* flight on some other cpu then we let it handle it. If we
		* were able to cancel the timer nothing can rearm it as we
		* own broadcast_lock.
		* This is called either from enter/exit idle code or from the
		* broadcast handler. In all cases tick_broadcast_lock is held.
		*
		* However we can also be called from the event handler of
		* ce_broadcast_hrtimer itself when it expires. We cannot
		* restart the timer because we are in the callback, but we
		* can set the expiry time and let the callback return
		* HRTIMER_RESTART.
		* hrtimer_cancel() cannot be called here neither from the
		* broadcast handler nor from the enter/exit idle code. The idle
		* code can run into the problem described in bc_shutdown() and the
		* broadcast handler cannot wait for itself to complete for obvious
		* reasons.
		*
		* Since we are in the idle loop at this point and because
		* hrtimer_{start/cancel} functions call into tracing,
		* calls to these functions must be bound within RCU_NONIDLE.
		* Each caller tries to arm the hrtimer on its own CPU, but if the
		* hrtimer callbback function is currently running, then
		* hrtimer_start() cannot move it and the timer stays on the CPU on
		* which it is assigned at the moment.
		*
		* As this can be called from idle code, the hrtimer_start()
		* invocation has to be wrapped with RCU_NONIDLE() as
		* hrtimer_start() can call into tracing.
		*/
		RCU_NONIDLE(
		{
		bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0;
		if (bc_moved) {
		hrtimer_start(&bctimer, expires,
		HRTIMER_MODE_ABS_PINNED_HARD);
		}
		}
		);

		if (bc_moved) {
		/* Bind the "device" to the cpu */
		bc->bound_on = smp_processor_id();
		} else if (bc->bound_on == smp_processor_id()) {
		hrtimer_set_expires(&bctimer, expires);
		}
		RCU_NONIDLE( {
		hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED_HARD);
		/*
		* The core tick broadcast mode expects bc->bound_on to be set
		* correctly to prevent a CPU which has the broadcast hrtimer
		* armed from going deep idle.
		*
		* As tick_broadcast_lock is held, nothing can change the cpu
		* base which was just established in hrtimer_start() above. So
		* the below access is safe even without holding the hrtimer
		* base lock.
		*/
		bc->bound_on = bctimer.base->cpu_base->cpu;
		} );
		return 0;
		}

		@@ -100,10 +100,6 @@ static enum hrtimer_restart bc_handler(struct hrtimer *t)
		{
		ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);

		if (clockevent_state_oneshot(&ce_broadcast_hrtimer))
		if (ce_broadcast_hrtimer.next_event != KTIME_MAX)
		return HRTIMER_RESTART;

		return HRTIMER_NORESTART;
		}

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