hrtimer: Move unmarked hrtimers to soft interrupt expiry on RT (f5c2f021) · Commits · 戴 / test

On PREEMPT_RT not all hrtimers can be expired in hard interrupt context even if that is perfectly fine on a PREEMPT_RT=n kernel, e.g. because they take regular spinlocks. Also for latency reasons PREEMPT_RT tries to defer most hrtimers' expiry into softirq context. hrtimers marked with HRTIMER_MODE_HARD must be kept in hard interrupt context expiry mode. Add the required logic. No functional change for PREEMPT_RT=n kernels. [ tglx: Split out of a larger combo patch. Added changelog ] Signed-off-by:

Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190726185753.551967692@linutronix.de

kernel/time/hrtimer.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -1275,8 +1275,17 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
		enum hrtimer_mode mode)
		{
		bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
		int base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
		struct hrtimer_cpu_base *cpu_base;
		int base;

		/*
		* On PREEMPT_RT enabled kernels hrtimers which are not explicitely
		* marked for hard interrupt expiry mode are moved into soft
		* interrupt context for latency reasons and because the callbacks
		* can invoke functions which might sleep on RT, e.g. spin_lock().
		*/
		if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
		softtimer = true;

		memset(timer, 0, sizeof(struct hrtimer));

		@@ -1290,6 +1299,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
		if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
		clock_id = CLOCK_MONOTONIC;

		base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
		base += hrtimer_clockid_to_base(clock_id);
		timer->is_soft = softtimer;
		timer->is_hard = !softtimer;

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