From: Paul E. McKenney <paulmck@kernel.org>
Date: Mon, 13 Dec 2021 19:05:07 +0000 (-0800)
Subject: rcu: Mark accesses to boost_starttime
X-Git-Tag: v6.1-rc5~1817^2^5~9
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a47f9f131dfe4f765e385fa90e13032eadb00bac;p=platform%2Fkernel%2Flinux-starfive.git

rcu: Mark accesses to boost_starttime

The boost_starttime shared variable has conflicting unmarked C-language
accesses, which are dangerous at best.  This commit therefore adds
appropriate marking.  This was found by KCSAN.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 422f7e4..829ae0b 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -997,7 +997,7 @@ static int rcu_torture_boost(void *arg)
 			goto checkwait;
 
 		/* Wait for the next test interval. */
-		oldstarttime = boost_starttime;
+		oldstarttime = READ_ONCE(boost_starttime);
 		while (time_before(jiffies, oldstarttime)) {
 			schedule_timeout_interruptible(oldstarttime - jiffies);
 			if (stutter_wait("rcu_torture_boost"))
@@ -1041,10 +1041,11 @@ static int rcu_torture_boost(void *arg)
 		 * interval.  Besides, we are running at RT priority,
 		 * so delays should be relatively rare.
 		 */
-		while (oldstarttime == boost_starttime && !kthread_should_stop()) {
+		while (oldstarttime == READ_ONCE(boost_starttime) && !kthread_should_stop()) {
 			if (mutex_trylock(&boost_mutex)) {
 				if (oldstarttime == boost_starttime) {
-					boost_starttime = jiffies + test_boost_interval * HZ;
+					WRITE_ONCE(boost_starttime,
+						   jiffies + test_boost_interval * HZ);
 					n_rcu_torture_boosts++;
 				}
 				mutex_unlock(&boost_mutex);