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From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:29:34 -0500
Subject: timers: Prepare for full preemption
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.9-rt3.tar.xz
When softirqs can be preempted we need to make sure that cancelling
the timer from the active thread can not deadlock vs. a running timer
callback. Add a waitqueue to resolve that.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/timer.h | 2 +-
kernel/time/timer.c | 5 +++--
2 files changed, 4 insertions(+), 3 deletions(-)
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -172,7 +172,7 @@ extern void add_timer(struct timer_list
extern int try_to_del_timer_sync(struct timer_list *timer);
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
extern int del_timer_sync(struct timer_list *timer);
#else
# define del_timer_sync(t) del_timer(t)
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1236,7 +1236,7 @@ int try_to_del_timer_sync(struct timer_l
}
EXPORT_SYMBOL(try_to_del_timer_sync);
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
static int __del_timer_sync(struct timer_list *timer)
{
struct timer_base *base;
@@ -1381,7 +1381,8 @@ static void expire_timers(struct timer_b
fn = timer->function;
- if (timer->flags & TIMER_IRQSAFE) {
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL) &&
+ timer->flags & TIMER_IRQSAFE) {
raw_spin_unlock(&base->lock);
call_timer_fn(timer, fn, baseclk);
base->running_timer = NULL;
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