lkml.org 
[lkml]   [2019]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:timers/core] hrtimer: Introduce HARD expiry mode
Commit-ID:  b04b3857625d7d91fd11fcc39da138d7602bfadd
Gitweb: https://git.kernel.org/tip/b04b3857625d7d91fd11fcc39da138d7602bfadd
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Fri, 26 Jul 2019 20:30:51 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 30 Jul 2019 23:57:53 +0200

hrtimer: Introduce HARD expiry mode

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 soft interrupt context.

But there are hrtimers which must be expired in hard interrupt context even
when PREEMPT_RT is enabled:

- hrtimers which must expiry in hard interrupt context, e.g. scheduler,
perf, watchdog related hrtimers

- latency critical hrtimers, e.g. nanosleep, ..., kvm lapic timer

Add a new mode flag HRTIMER_MODE_HARD which allows to mark these timers so
PREEMPT_RT will not move them into softirq expiry mode.

[ 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/20190726185752.981398465@linutronix.de

---
include/linux/hrtimer.h | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 24072a0942c0..15c2ba6b6316 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -38,6 +38,7 @@ enum hrtimer_mode {
HRTIMER_MODE_REL = 0x01,
HRTIMER_MODE_PINNED = 0x02,
HRTIMER_MODE_SOFT = 0x04,
+ HRTIMER_MODE_HARD = 0x08,

HRTIMER_MODE_ABS_PINNED = HRTIMER_MODE_ABS | HRTIMER_MODE_PINNED,
HRTIMER_MODE_REL_PINNED = HRTIMER_MODE_REL | HRTIMER_MODE_PINNED,
@@ -48,6 +49,11 @@ enum hrtimer_mode {
HRTIMER_MODE_ABS_PINNED_SOFT = HRTIMER_MODE_ABS_PINNED | HRTIMER_MODE_SOFT,
HRTIMER_MODE_REL_PINNED_SOFT = HRTIMER_MODE_REL_PINNED | HRTIMER_MODE_SOFT,

+ HRTIMER_MODE_ABS_HARD = HRTIMER_MODE_ABS | HRTIMER_MODE_HARD,
+ HRTIMER_MODE_REL_HARD = HRTIMER_MODE_REL | HRTIMER_MODE_HARD,
+
+ HRTIMER_MODE_ABS_PINNED_HARD = HRTIMER_MODE_ABS_PINNED | HRTIMER_MODE_HARD,
+ HRTIMER_MODE_REL_PINNED_HARD = HRTIMER_MODE_REL_PINNED | HRTIMER_MODE_HARD,
};

/*
\
 
 \ /
  Last update: 2019-07-31 00:11    [W:0.161 / U:3.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site