rcutorture: Remove extraneous rcu_torture_pipe_update_one() READ_ONCE()

paulmckrcu · urezki · commit 8d0f9a6639f5 · 2024-04-16T11:16:25.000+02:00
The rcu_torture_pipe_update_one() cannot run concurrently with any updates of ->rtort_pipe_count, so this commit removes the extraneous READ_ONCE() from the read from this field. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Closes: https://lore.kernel.org/lkml/CAHk-=wiX_zF5Mpt8kUm_LFQpYY-mshrXJPOe+wKNwiVhEUcU9g@mail.gmail.com/ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
@@ -461,7 +461,7 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)
 		WRITE_ONCE(rp->rtort_chkp, NULL);
 		smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().
 	}
-	i = READ_ONCE(rp->rtort_pipe_count);
+	i = rp->rtort_pipe_count;
 	if (i > RCU_TORTURE_PIPE_LEN)
 		i = RCU_TORTURE_PIPE_LEN;
 	atomic_inc(&rcu_torture_wcount[i]);

Original file line number	Diff line number	Diff line change
`@@ -461,7 +461,7 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)`
`461`	`461`	`WRITE_ONCE(rp->rtort_chkp, NULL);`
`462`	`462`	`smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().`
`463`	`463`	`}`
`464`		`- i = READ_ONCE(rp->rtort_pipe_count);`
	`464`	`+ i = rp->rtort_pipe_count;`
`465`	`465`	`if (i > RCU_TORTURE_PIPE_LEN)`
`466`	`466`	`i = RCU_TORTURE_PIPE_LEN;`
`467`	`467`	`atomic_inc(&rcu_torture_wcount[i]);`