linux-kernel - [PATCH] locking/ww_mutex: Initialize waiter.ww

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Message-ID: <20210819180850.koqw3ujmxga5wo4n@linutronix.de>
Date:   Thu, 19 Aug 2021 20:08:50 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <efault@....de>
Subject: [PATCH] locking/ww_mutex: Initialize waiter.ww_ctx properly

The gathering of the debug code for the ww-mutex initialized moved the
POISON initialiation into one spot and only set waiter.ww_ctx if the
ww_ctx was non-NULL thus keeping the POISON value in ww-mutex case.

For ww-mutex without a context it is expected to set the context to
NULL, the poison value was intended only for the regular mutex.

Move the waiter.ww_ctx where it was previously so it is initialized to
NULL if no ww_ctx was passed.

Fixes: c0afb0ffc06e6 ("locking/ww_mutex: Gather mutex_waiter initialization")
Reported-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/locking/mutex.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 05b68931622d1..d1068b0b163af 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -614,8 +614,6 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 
 	debug_mutex_lock_common(lock, &waiter);
 	waiter.task = current;
-	if (ww_ctx)
-		waiter.ww_ctx = ww_ctx;
 
 	lock_contended(&lock->dep_map, ip);
 
@@ -630,6 +628,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 		ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
 		if (ret)
 			goto err_early_kill;
+		waiter.ww_ctx = ww_ctx;
 	}
 
 	set_current_state(state);
-- 
2.33.0