From: Paul E. McKenney <paulmck@kernel.org>
Date: Thu, 3 Jun 2021 17:17:36 +0000 (-0700)
Subject: rcu: Mark lockless ->qsmask read in rcu_check_boost_fail()
X-Git-Tag: accepted/tizen/unified/20230118.172025~6579^2^2~7
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d9ee962feb4f26d4eac0042861457d941aa2df5f;p=platform%2Fkernel%2Flinux-rpi.git

rcu: Mark lockless ->qsmask read in rcu_check_boost_fail()

Accesses to ->qsmask are normally protected by ->lock, but there is an
exception in the diagnostic code in rcu_check_boost_fail().  This commit
therefore applies data_race() to this access to avoid KCSAN complaining
about the C-language writes protected by ->lock.

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

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 42847ca..6dd6c9a 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -766,7 +766,7 @@ bool rcu_check_boost_fail(unsigned long gp_state, int *cpup)
 
 	rcu_for_each_leaf_node(rnp) {
 		if (!cpup) {
-			if (READ_ONCE(rnp->qsmask)) {
+			if (data_race(READ_ONCE(rnp->qsmask))) {
 				return false;
 			} else {
 				if (READ_ONCE(rnp->gp_tasks))