linux-kernel - [PATCH RT 1/2] locking/rwsem-rt: Remove might_sleep() in __up

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Date:   Thu,  2 Sep 2021 15:26:30 -0500
From:   zanussi@...nel.org
To:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Daniel Wagner <wagi@...om.org>,
        Clark Williams <williams@...hat.com>,
        "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>
Cc:     Andrew Halaney <ahalaney@...hat.com>
Subject: [PATCH RT 1/2] locking/rwsem-rt: Remove might_sleep() in __up_read()

From: Andrew Halaney <ahalaney@...hat.com>

v5.4.143-rt64-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


[ Upstream commit b2ed0a4302faf2bb09e97529dd274233c082689b ]

There's no chance of sleeping here, the reader is giving up the
lock and possibly waking up the writer who is waiting on it.

Reported-by: Chunyu Hu <chuhu@...hat.com>
Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Tom Zanussi <zanussi@...nel.org>
---
 kernel/locking/rwsem-rt.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c
index 19ea20be3fd7..966946454ced 100644
--- a/kernel/locking/rwsem-rt.c
+++ b/kernel/locking/rwsem-rt.c
@@ -200,7 +200,6 @@ void __up_read(struct rw_semaphore *sem)
 	if (!atomic_dec_and_test(&sem->readers))
 		return;
 
-	might_sleep();
 	raw_spin_lock_irq(&m->wait_lock);
 	/*
 	 * Wake the writer, i.e. the rtmutex owner. It might release the
-- 
2.17.1