Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Tom Zanussi <tom.zanussi@linux.intel.com>
To:     linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Cc:     rostedt@goodmis.org, tglx@linutronix.de, C.Emde@osadl.org,
        jkacur@redhat.com, bigeasy@linutronix.de,
        daniel.wagner@siemens.com, julia@ni.com, stable-rt@vger.kernel.org,
        Daniel Wagner <wagi@monom.org>,
        Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: [PATCH 03/15] posix-timers: move the rcu head out of the union
Date:   Thu,  2 Aug 2018 17:25:18 -0500
Message-Id: <a2a99b774ea6502023e6bc0dffed1ce5c14c74ae.1533242791.git.tom.zanussi@linux.intel.com>
In-Reply-To: <cover.1533242791.git.tom.zanussi@linux.intel.com>
References: <cover.1533242791.git.tom.zanussi@linux.intel.com>
In-Reply-To: <cover.1533242791.git.tom.zanussi@linux.intel.com>
References: <cover.1533242791.git.tom.zanussi@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Wagner <wagi@monom.org>
(cherry picked from commit 57f93c5f597fa32af860321c5bca34bc5ffe08e1)
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/posix-timers.h | 2 +-
 kernel/time/posix-timers.c   | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 907f3fd191ac..e2e43c61f6a1 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -92,8 +92,8 @@ struct k_itimer {
 			struct alarm alarmtimer;
 			ktime_t interval;
 		} alarm;
-		struct rcu_head rcu;
 	} it;
+	struct rcu_head rcu;
 };
 
 struct k_clock {
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index b5e0ff549422..bdf91054e6c3 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -560,7 +560,7 @@ static struct k_itimer * alloc_posix_timer(void)
 
 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);
 }
@@ -577,7 +577,7 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
 	}
 	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 struct k_clock *clockid_to_kclock(const clockid_t id)
-- 
2.14.1