| Date | Fri, 26 Jul 2019 20:30:57 +0200 | From | Thomas Gleixner <> | Subject | [patch 09/12] hrtimer: Move unmarked hrtimers to soft interrupt expiry on RT |
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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> --- kernel/time/hrtimer.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1271,8 +1271,16 @@ static void __hrtimer_init(struct hrtime 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. + */ + if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD)) + softtimer = true; memset(timer, 0, sizeof(struct hrtimer)); @@ -1286,6 +1294,7 @@ static void __hrtimer_init(struct hrtime 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->base = &cpu_base->clock_base[base];
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