Commit-ID: edd2f987491fb47949a9612743435d6d0f61f614 Gitweb: https://git.kernel.org/tip/edd2f987491fb47949a9612743435d6d0f61f614 Author: Sebastian Andrzej Siewior <[email protected]> AuthorDate: Fri, 26 Jul 2019 20:30:57 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 1 Aug 2019 17:43:19 +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 <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- 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;
