Commit 1c143c4b authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

locking/rtmutex: Provide the spin/rwlock core lock function 



A simplified version of the rtmutex slowlock function, which neither handles
signals nor timeouts, and is careful about preserving the state of the
blocked task across the lock operation.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.770228446@linutronix.de
parent 342a9324

kernel/locking/rtmutex.c

+60 −0
Original line number Diff line number Diff line
@@ -1416,3 +1416,63 @@ static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock, 
	return rt_mutex_slowlock(lock, state);

}

#endif /* RT_MUTEX_BUILD_MUTEX */



#ifdef RT_MUTEX_BUILD_SPINLOCKS

/*

 * Functions required for spin/rw_lock substitution on RT kernels

 */



/**

 * rtlock_slowlock_locked - Slow path lock acquisition for RT locks

 * @lock:	The underlying RT mutex

 */

static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock)

{

	struct rt_mutex_waiter waiter;



	lockdep_assert_held(&lock->wait_lock);



	if (try_to_take_rt_mutex(lock, current, NULL))

		return;



	rt_mutex_init_rtlock_waiter(&waiter);



	/* Save current state and set state to TASK_RTLOCK_WAIT */

	current_save_and_set_rtlock_wait_state();



	task_blocks_on_rt_mutex(lock, &waiter, current, RT_MUTEX_MIN_CHAINWALK);



	for (;;) {

		/* Try to acquire the lock again */

		if (try_to_take_rt_mutex(lock, current, &waiter))

			break;



		raw_spin_unlock_irq(&lock->wait_lock);



		schedule_rtlock();



		raw_spin_lock_irq(&lock->wait_lock);

		set_current_state(TASK_RTLOCK_WAIT);

	}



	/* Restore the task state */

	current_restore_rtlock_saved_state();



	/*

	 * try_to_take_rt_mutex() sets the waiter bit unconditionally.

	 * We might have to fix that up:

	 */

	fixup_rt_mutex_waiters(lock);

	debug_rt_mutex_free_waiter(&waiter);

}



static __always_inline void __sched rtlock_slowlock(struct rt_mutex_base *lock)

{

	unsigned long flags;



	raw_spin_lock_irqsave(&lock->wait_lock, flags);

	rtlock_slowlock_locked(lock);

	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);

}



#endif /* RT_MUTEX_BUILD_SPINLOCKS */

kernel/locking/rtmutex_common.h

+1 −1
Original line number Diff line number Diff line
@@ -181,7 +181,7 @@ static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) 
	waiter->task = NULL;

}



static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter)

static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)

{

	rt_mutex_init_waiter(waiter);

	waiter->wake_state = TASK_RTLOCK_WAIT;