linux-kernel - [PATCH 3/8] rcu/exp: Fix RCU expedited parallel grace period kworker allocation failure recovery

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Date:   Fri,  8 Dec 2023 23:05:40 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Neeraj Upadhyay <neeraj.upadhyay@....com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>, rcu <rcu@...r.kernel.org>,
        Anna-Maria Behnsen <anna-maria.behnsen@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kalesh Singh <kaleshsingh@...gle.com>
Subject: [PATCH 3/8] rcu/exp: Fix RCU expedited parallel grace period kworker allocation failure recovery

Under CONFIG_RCU_EXP_KTHREAD=y, the nodes initialization for expedited
grace periods is queued to a kworker. However if the allocation of that
kworker failed, the nodes initialization is performed synchronously by
the caller instead.

Now the check for kworker initialization failure relies on the kworker
pointer to be NULL while its value might actually encapsulate an
allocation failure error.

Make sure to handle this case.

Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker")
Cc: Kalesh Singh <kaleshsingh@...gle.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 kernel/rcu/tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 82f8130d3fe3..055f4817bc70 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4723,6 +4723,7 @@ static void __init rcu_start_exp_gp_kworkers(void)
 	rcu_exp_par_gp_kworker = kthread_create_worker(0, par_gp_kworker_name);
 	if (IS_ERR_OR_NULL(rcu_exp_par_gp_kworker)) {
 		pr_err("Failed to create %s!\n", par_gp_kworker_name);
+		rcu_exp_par_gp_kworker = NULL;
 		kthread_destroy_worker(rcu_exp_gp_kworker);
 		return;
 	}
-- 
2.42.1