linux-kernel - [PATCH] rcu/srcutiny: don't return before reenabling preemption

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Message-ID: <20241007101415.466155-1-mschmidt@redhat.com>
Date: Mon,  7 Oct 2024 12:14:15 +0200
From: Michal Schmidt <mschmidt@...hat.com>
To: Lai Jiangshan <jiangshanlai@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc: rcu@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] rcu/srcutiny: don't return before reenabling preemption

Code after the return statement is dead. Enable preemption before
returning from srcu_drive_gp().

This will be important when/if PREEMPT_AUTO (lazy resched) gets merged.

Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
Signed-off-by: Michal Schmidt <mschmidt@...hat.com>
---
 kernel/rcu/srcutiny.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 549c03336ee9..4dcbf8aa80ff 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -122,8 +122,8 @@ void srcu_drive_gp(struct work_struct *wp)
 	ssp = container_of(wp, struct srcu_struct, srcu_work);
 	preempt_disable();  // Needed for PREEMPT_AUTO
 	if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) {
-		return; /* Already running or nothing to do. */
 		preempt_enable();
+		return; /* Already running or nothing to do. */
 	}
 
 	/* Remove recently arrived callbacks and wait for readers. */
-- 
2.46.2