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locking/rtmutex: Avoid unconditional slowpath for DEBUG_RT_MUTEXES 

With DEBUG_RT_MUTEXES enabled the fast-path rt_mutex_cmpxchg_acquire()
always fails and all lock operations take the slow path.

Provide a new helper inline rt_mutex_try_acquire() which maps to
rt_mutex_cmpxchg_acquire() in the non-debug case. For the debug case
it invokes rt_mutex_slowtrylock() which can acquire a non-contended
rtmutex under full debug coverage.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230908162254.999499-3-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2023-09-08 18:22:49 +02:00 committed by Peter Zijlstra
parent 28bc55f654
commit af9f006393
2 changed files with 21 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
kernel/locking/rtmutex.c
View File

@ -218,6 +218,11 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock,
return try_cmpxchg_acquire(&lock->owner, &old, new);
}
static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock)
{
return rt_mutex_cmpxchg_acquire(lock, NULL, current);
}
static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
struct task_struct *old,
struct task_struct *new)
@ -297,6 +302,20 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock,
}
static int __sched rt_mutex_slowtrylock(struct rt_mutex_base *lock);
static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock)
{
/*
* With debug enabled rt_mutex_cmpxchg trylock() will always fail.
*
* Avoid unconditionally taking the slow path by using
* rt_mutex_slow_trylock() which is covered by the debug code and can
* acquire a non-contended rtmutex.
*/
return rt_mutex_slowtrylock(lock);
}
static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
struct task_struct *old,
struct task_struct *new)
@ -1755,7 +1774,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
unsigned int state)
{
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
if (likely(rt_mutex_try_acquire(lock)))
return 0;
return rt_mutex_slowlock(lock, NULL, state);

2
kernel/locking/ww_rt_mutex.c
View File

@ -62,7 +62,7 @@ __ww_rt_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx,
}
mutex_acquire_nest(&rtm->dep_map, 0, 0, nest_lock, ip);
if (likely(rt_mutex_cmpxchg_acquire(&rtm->rtmutex, NULL, current))) {
if (likely(rt_mutex_try_acquire(&rtm->rtmutex))) {
if (ww_ctx)
ww_mutex_set_context_fastpath(lock, ww_ctx);
return 0;