diff mbox series

[07/32] rcu-tasks: Make trc_read_check_handler() fetch ->trc_reader_nesting only once

Message ID 20220620225411.3842519-7-paulmck@kernel.org (mailing list archive)
State Mainlined
Commit 9ff86b4c443cc93bf3a9b624e3385e4114388e85
Headers show
Series RCU Tasks updates for v5.20 | expand

Commit Message

Paul E. McKenney June 20, 2022, 10:53 p.m. UTC 
This commit replaces the pair of READ_ONCE(t->trc_reader_nesting) calls
with a single such call and a local variable.  This makes the code's
intent more clear.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
---
 kernel/rcu/tasks.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 561d24f7f73cc..8fe78a7fecafd 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1278,6 +1278,7 @@  static void trc_del_holdout(struct task_struct *t)
 /* IPI handler to check task state. */
 static void trc_read_check_handler(void *t_in)
 {
+	int nesting;
 	struct task_struct *t = current;
 	struct task_struct *texp = t_in;
 
@@ -1287,12 +1288,13 @@  static void trc_read_check_handler(void *t_in)
 
 	// If the task is not in a read-side critical section, and
 	// if this is the last reader, awaken the grace-period kthread.
-	if (likely(!READ_ONCE(t->trc_reader_nesting))) {
+	nesting = READ_ONCE(t->trc_reader_nesting);
+	if (likely(!nesting)) {
 		rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
 		goto reset_ipi;
 	}
 	// If we are racing with an rcu_read_unlock_trace(), try again later.
-	if (unlikely(READ_ONCE(t->trc_reader_nesting) < 0))
+	if (unlikely(nesting < 0))
 		goto reset_ipi;
 
 	// Get here if the task is in a read-side critical section.  Set