Messages in this thread Patch in this message | | | Date | Tue, 30 Jul 2019 15:15:43 -0700 | From | tip-bot for Sebastian Andrzej Siewior <> | Subject | [tip:timers/core] hrtimer: Move unmarked hrtimers to soft interrupt expiry on RT |
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Commit-ID: f4f9a0e3f4c01a11043aca77006532c3c889c9ba Gitweb: https://git.kernel.org/tip/f4f9a0e3f4c01a11043aca77006532c3c889c9ba Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> AuthorDate: Fri, 26 Jul 2019 20:30:57 +0200 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Tue, 30 Jul 2019 23:57:56 +0200
hrtimer: Move unmarked hrtimers to soft interrupt expiry on RT
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 | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 0ace301a56f4..90dcc4d95e91 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -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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