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locking/rtmutex: Consolidate the fast/slowpath invocation

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The indirection via a function pointer (which is at least optimized into a
tail call by the compiler) is making the code hard to read.

Clean it up and move the futex related trylock functions down to the futex
section.

Move the wake_q wakeup into rt_mutex_slowunlock(). No point in handing it
to the caller. The futex code uses a different function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210326153944.247927548@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-03-26 16:29:41 +01:00 committed by Ingo Molnar
parent d7a2edb890
commit 70c80103aa
1 changed files with 60 additions and 86 deletions
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146
kernel/locking/rtmutex.c
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@ -1298,14 +1298,25 @@ static int __sched rt_mutex_slowtrylock(struct rt_mutex *lock)
return ret;
}
/*
* Performs the wakeup of the top-waiter and re-enables preemption.
*/
void __sched rt_mutex_postunlock(struct wake_q_head *wake_q)
{
wake_up_q(wake_q);
/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
preempt_enable();
}
/*
* Slow path to release a rt-mutex.
*
* Return whether the current task needs to call rt_mutex_postunlock().
*/
static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
struct wake_q_head *wake_q)
static void __sched rt_mutex_slowunlock(struct rt_mutex *lock)
{
DEFINE_WAKE_Q(wake_q);
unsigned long flags;
/* irqsave required to support early boot calls */
@ -1347,7 +1358,7 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
while (!rt_mutex_has_waiters(lock)) {
/* Drops lock->wait_lock ! */
if (unlock_rt_mutex_safe(lock, flags) == true)
return false;
return;
/* Relock the rtmutex and try again */
raw_spin_lock_irqsave(&lock->wait_lock, flags);
}
@ -1358,10 +1369,10 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
*
* Queue the next waiter for wakeup once we release the wait_lock.
*/
mark_wakeup_next_waiter(wake_q, lock);
mark_wakeup_next_waiter(&wake_q, lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return true; /* call rt_mutex_postunlock() */
rt_mutex_postunlock(&wake_q);
}
/*
@ -1370,60 +1381,21 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
* The atomic acquire/release ops are compiled away, when either the
* architecture does not support cmpxchg or when debugging is enabled.
*/
static __always_inline int
rt_mutex_fastlock(struct rt_mutex *lock, int state,
int (*slowfn)(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
enum rtmutex_chainwalk chwalk))
static __always_inline int __rt_mutex_lock(struct rt_mutex *lock, long state,
unsigned int subclass)
{
int ret;
might_sleep();
mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 0;
return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
}
static __always_inline int
rt_mutex_fasttrylock(struct rt_mutex *lock,
int (*slowfn)(struct rt_mutex *lock))
{
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 1;
return slowfn(lock);
}
/*
* Performs the wakeup of the top-waiter and re-enables preemption.
*/
void __sched rt_mutex_postunlock(struct wake_q_head *wake_q)
{
wake_up_q(wake_q);
/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
preempt_enable();
}
static __always_inline void
rt_mutex_fastunlock(struct rt_mutex *lock,
bool (*slowfn)(struct rt_mutex *lock,
struct wake_q_head *wqh))
{
DEFINE_WAKE_Q(wake_q);
if (likely(rt_mutex_cmpxchg_release(lock, current, NULL)))
return;
if (slowfn(lock, &wake_q))
rt_mutex_postunlock(&wake_q);
}
static __always_inline void __rt_mutex_lock(struct rt_mutex *lock,
unsigned int subclass)
{
might_sleep();
mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
ret = rt_mutex_slowlock(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
if (ret)
mutex_release(&lock->dep_map, _RET_IP_);
return ret;
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@ -1435,7 +1407,7 @@ static __always_inline void __rt_mutex_lock(struct rt_mutex *lock,
*/
void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
{
__rt_mutex_lock(lock, subclass);
__rt_mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);
@ -1448,7 +1420,7 @@ EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);
*/
void __sched rt_mutex_lock(struct rt_mutex *lock)
{
__rt_mutex_lock(lock, 0);
__rt_mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock);
#endif
@ -1464,42 +1436,21 @@ EXPORT_SYMBOL_GPL(rt_mutex_lock);
*/
int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
{
int ret;
might_sleep();
mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
ret = rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock);
if (ret)
mutex_release(&lock->dep_map, _RET_IP_);
return ret;
return __rt_mutex_lock(lock, TASK_INTERRUPTIBLE, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
/*
* Futex variant, must not use fastpath.
*/
int __sched rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return rt_mutex_slowtrylock(lock);
}
int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return __rt_mutex_slowtrylock(lock);
}
/**
* rt_mutex_trylock - try to lock a rt_mutex
*
* @lock: the rt_mutex to be locked
*
* This function can only be called in thread context. It's safe to
* call it from atomic regions, but not from hard interrupt or soft
* interrupt context.
* This function can only be called in thread context. It's safe to call it
* from atomic regions, but not from hard or soft interrupt context.
*
* Returns 1 on success and 0 on contention
* Returns:
* 1 on success
* 0 on contention
*/
int __sched rt_mutex_trylock(struct rt_mutex *lock)
{
@ -1508,7 +1459,14 @@ int __sched rt_mutex_trylock(struct rt_mutex *lock)
if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
return 0;
ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
/*
* No lockdep annotation required because lockdep disables the fast
* path.
*/
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 1;
ret = rt_mutex_slowtrylock(lock);
if (ret)
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
@ -1524,10 +1482,26 @@ EXPORT_SYMBOL_GPL(rt_mutex_trylock);
void __sched rt_mutex_unlock(struct rt_mutex *lock)
{
mutex_release(&lock->dep_map, _RET_IP_);
rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
if (likely(rt_mutex_cmpxchg_release(lock, current, NULL)))
return;
rt_mutex_slowunlock(lock);
}
EXPORT_SYMBOL_GPL(rt_mutex_unlock);
/*
* Futex variants, must not use fastpath.
*/
int __sched rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return rt_mutex_slowtrylock(lock);
}
int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return __rt_mutex_slowtrylock(lock);
}
/**
* __rt_mutex_futex_unlock - Futex variant, that since futex variants
* do not use the fast-path, can be simple and will not need to retry.