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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 27 May 2019 16:54:05 +0200
Subject: [PATCH] posix-timers: move rcu out of union
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.17-rt9.tar.xz
On RT the timer can be preempted while running and therefore we wait
with timer_wait_for_callback() for the timer to complete (instead of
busy looping). The RCU-readlock is held to ensure that this posix timer
is not removed while we wait on it.
If the timer is removed then it invokes call_rcu() with a pointer that
is shared with the hrtimer because it is part of the same union.
In order to avoid any possible side effects I am moving the rcu pointer
out of the union.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/posix-timers.h | 2 +-
kernel/time/posix-timers.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -114,8 +114,8 @@ struct k_itimer {
struct {
struct alarm alarmtimer;
} alarm;
- struct rcu_head rcu;
} it;
+ struct rcu_head rcu;
};
void run_posix_cpu_timers(struct task_struct *task);
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -442,7 +442,7 @@ static struct k_itimer * alloc_posix_tim
static void k_itimer_rcu_free(struct rcu_head *head)
{
- struct k_itimer *tmr = container_of(head, struct k_itimer, it.rcu);
+ struct k_itimer *tmr = container_of(head, struct k_itimer, rcu);
kmem_cache_free(posix_timers_cache, tmr);
}
@@ -459,7 +459,7 @@ static void release_posix_timer(struct k
}
put_pid(tmr->it_pid);
sigqueue_free(tmr->sigq);
- call_rcu(&tmr->it.rcu, k_itimer_rcu_free);
+ call_rcu(&tmr->rcu, k_itimer_rcu_free);
}
static int common_timer_create(struct k_itimer *new_timer)
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