From: Peter Zijlstra <peterz@infradead.org>
To: mingo@redhat.com, longman@redhat.com, boqun.feng@gmail.com,
will@kernel.org
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
yanfei.xu@windriver.com
Subject: [RFC][PATCH 1/4] locking/mutex: Use try_cmpxchg()
Date: Wed, 30 Jun 2021 17:35:17 +0200 [thread overview]
Message-ID: <20210630154114.834438545@infradead.org> (raw)
In-Reply-To: 20210630153516.832731403@infradead.org
For simpler and better code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/locking/mutex.c | 27 ++++++---------------------
1 file changed, 6 insertions(+), 21 deletions(-)
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -100,7 +100,7 @@ static inline struct task_struct *__mute
owner = atomic_long_read(&lock->owner);
for (;;) { /* must loop, can race against a flag */
- unsigned long old, flags = __owner_flags(owner);
+ unsigned long flags = __owner_flags(owner);
unsigned long task = owner & ~MUTEX_FLAGS;
if (task) {
@@ -124,11 +124,8 @@ static inline struct task_struct *__mute
*/
flags &= ~MUTEX_FLAG_HANDOFF;
- old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);
- if (old == owner)
+ if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, curr | flags))
return NULL;
-
- owner = old;
}
return __owner_task(owner);
@@ -168,10 +165,7 @@ static __always_inline bool __mutex_unlo
{
unsigned long curr = (unsigned long)current;
- if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr)
- return true;
-
- return false;
+ return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
}
#endif
@@ -226,7 +220,7 @@ static void __mutex_handoff(struct mutex
unsigned long owner = atomic_long_read(&lock->owner);
for (;;) {
- unsigned long old, new;
+ unsigned long new;
#ifdef CONFIG_DEBUG_MUTEXES
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
@@ -238,11 +232,8 @@ static void __mutex_handoff(struct mutex
if (task)
new |= MUTEX_FLAG_PICKUP;
- old = atomic_long_cmpxchg_release(&lock->owner, owner, new);
- if (old == owner)
+ if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new))
break;
-
- owner = old;
}
}
@@ -1237,8 +1228,6 @@ static noinline void __sched __mutex_unl
*/
owner = atomic_long_read(&lock->owner);
for (;;) {
- unsigned long old;
-
#ifdef CONFIG_DEBUG_MUTEXES
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
@@ -1247,16 +1236,12 @@ static noinline void __sched __mutex_unl
if (owner & MUTEX_FLAG_HANDOFF)
break;
- old = atomic_long_cmpxchg_release(&lock->owner, owner,
- __owner_flags(owner));
- if (old == owner) {
+ if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) {
if (owner & MUTEX_FLAG_WAITERS)
break;
return;
}
-
- owner = old;
}
spin_lock(&lock->wait_lock);
next prev parent reply other threads:[~2021-06-30 15:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-30 15:35 [RFC][PATCH 0/4] locking/mutex: Some HANDOFF fixes Peter Zijlstra
2021-06-30 15:35 ` Peter Zijlstra [this message]
2021-07-05 11:59 ` [RFC][PATCH 1/4] locking/mutex: Use try_cmpxchg() Xu, Yanfei
2021-07-05 14:00 ` Peter Zijlstra
2021-07-05 14:52 ` Xu, Yanfei
2021-07-05 15:07 ` [PATCH] Documentation/atomic_t: Document cmpxchg() vs try_cmpxchg() Peter Zijlstra
2021-07-05 15:21 ` Will Deacon
2021-07-05 15:25 ` Xu, Yanfei
2021-07-05 17:12 ` Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] locking/mutex: Use try_cmpxchg() tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 2/4] locking/mutex: Fix HANDOFF condition Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 3/4] locking/mutex: Introduce __mutex_trylock_or_handoff() Peter Zijlstra
2021-06-30 16:30 ` Waiman Long
2021-06-30 18:04 ` Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 4/4] locking/mutex: Add MUTEX_WARN_ON Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 19:03 ` [RFC][PATCH 0/4] locking/mutex: Some HANDOFF fixes Waiman Long
2021-07-01 2:11 ` Xu, Yanfei
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