linux-kernel - [PATCH rcu 7/8] torture: Wake up kthreads after storing task

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Message-Id: <20220204235327.2948-7-paulmck@kernel.org>
Date:   Fri,  4 Feb 2022 15:53:26 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Uladzislau Rezki <urezki@...il.com>
Subject: [PATCH rcu 7/8] torture: Wake up kthreads after storing task_struct pointer

Currently, _torture_create_kthread() uses kthread_run() to create
torture-test kthreads, which means that the resulting task_struct
pointer is stored after the newly created kthread has been marked
runnable.  This in turn can cause spurious failure of checks for
code being run by a particular kthread.  This commit therefore changes
_torture_create_kthread() to use kthread_create(), then to do an explicit
wake_up_process() after the task_struct pointer has been stored.

Reported-by: Frederic Weisbecker <frederic@...nel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@...cinc.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/torture.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/torture.c b/kernel/torture.c
index f55d803f995d4..789aeb0e1159c 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -931,12 +931,14 @@ int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 	int ret = 0;
 
 	VERBOSE_TOROUT_STRING(m);
-	*tp = kthread_run(fn, arg, "%s", s);
+	*tp = kthread_create(fn, arg, "%s", s);
 	if (IS_ERR(*tp)) {
 		ret = PTR_ERR(*tp);
 		TOROUT_ERRSTRING(f);
 		*tp = NULL;
+		return ret;
 	}
+	wake_up_process(*tp);  // Process is sleeping, so ordering provided.
 	torture_shuffle_task_register(*tp);
 	return ret;
 }
-- 
2.31.1.189.g2e36527f23