Messages in this thread Patch in this message | | | From | Sebastian Andrzej Siewior <> | Subject | [PATCH RT] time/hrtimer: Use softirq based wakeups for non-RT threads | Date | Wed, 4 Oct 2017 18:08:20 +0200 |
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Normal wake ups (like clock_nanosleep()) which are performed by normal users can easily lead to 2ms latency spikes if (enough) hrtimer wakeups are synchronized. This patch moves all hrtimers wakeups to the softirq queue unless the caller has a RT priority.
Reported-by: Gratian Crisan <gratian.crisan@ni.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/time/hrtimer.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 3aa823fcab70..8ea2825a50af 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1622,14 +1622,31 @@ static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer) return HRTIMER_NORESTART; } +#ifdef CONFIG_PREEMPT_RT_FULL +static bool task_is_elevated(struct task_struct *tsk) +{ + int policy = tsk->policy; + + if (policy == SCHED_FIFO || policy == SCHED_RR) + return true; + if (policy == SCHED_DEADLINE) + return true; + return false; +} +#endif + static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl, clockid_t clock_id, enum hrtimer_mode mode, struct task_struct *task) { #ifdef CONFIG_PREEMPT_RT_FULL - if (!(clock_id & HRTIMER_BASE_SOFT_MASK)) - clock_id |= HRTIMER_BASE_HARD_MASK; + if (!(clock_id & (HRTIMER_BASE_HARD_MASK | HRTIMER_BASE_SOFT_MASK))) { + if (task_is_elevated(current) || system_state != SYSTEM_RUNNING) + clock_id |= HRTIMER_BASE_HARD_MASK; + else + clock_id |= HRTIMER_BASE_SOFT_MASK; + } #endif __hrtimer_init(&sl->timer, clock_id, mode); sl->timer.function = hrtimer_wakeup; -- 2.14.2
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