linux-kernel - [RFC PATCH 06/11] kernel/locking: Expose mutex

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Message-ID: <20221003214501.2050087-7-connoro@google.com>
Date:   Mon,  3 Oct 2022 21:44:56 +0000
From:   "Connor O'Brien" <connoro@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, John Stultz <jstultz@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Qais Yousef <qais.yousef@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        "Connor O'Brien" <connoro@...gle.com>
Subject: [RFC PATCH 06/11] kernel/locking: Expose mutex_owner()

From: Juri Lelli <juri.lelli@...hat.com>

Implementing proxy execution requires that scheduler code be able to
identify the current owner of a mutex. Expose a new helper
mutex_owner() for this purpose.

Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
[Removed the EXPORT_SYMBOL]
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Connor O'Brien <connoro@...gle.com>
---
 include/linux/mutex.h  | 2 ++
 kernel/locking/mutex.c | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 8f226d460f51..ebdc59cb0bf6 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -118,6 +118,8 @@ do {									\
 extern void __mutex_init(struct mutex *lock, const char *name,
 			 struct lock_class_key *key);
 
+extern struct task_struct *mutex_owner(struct mutex *lock);
+
 /**
  * mutex_is_locked - is the mutex locked
  * @lock: the mutex to be queried
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index f39e9ee3c4d0..325fc9db5004 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -81,6 +81,11 @@ static inline struct task_struct *__mutex_owner(struct mutex *lock)
 	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
 }
 
+struct task_struct *mutex_owner(struct mutex *lock)
+{
+	return __mutex_owner(lock);
+}
+
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
 	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
-- 
2.38.0.rc1.362.ged0d419d3c-goog