linux-kernel - [PATCH] rcu: Fix opposite might_sleep() check in rcu_blocking_is

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Message-Id: <20221215035755.2820163-1-qiang1.zhang@intel.com>
Date:   Thu, 15 Dec 2022 11:57:55 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        joel@...lfernandes.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu: Fix opposite might_sleep() check in rcu_blocking_is_gp()

Currently, if the system is in the RCU_SCHEDULER_INACTIVE state, invoke
synchronize_rcu_*() will implies a grace period and return directly,
so there is no sleep action due to waiting for a grace period to end,
but this might_sleep() check is the opposite. therefore, this commit
puts might_sleep() check in the correct palce.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ee8a6a711719..65f3dd2fd3ae 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3379,9 +3379,10 @@ void __init kfree_rcu_scheduler_running(void)
  */
 static int rcu_blocking_is_gp(void)
 {
-	if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
+	if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) {
+		might_sleep();
 		return false;
-	might_sleep();  /* Check for RCU read-side critical section. */
+	}
 	return true;
 }
 
-- 
2.25.1