locking/refcounts: Implement refcount_dec_and_lock_irqsave() (7ea959c4) · Commits · 戴 / test

There are in-tree users of refcount_dec_and_lock() which must acquire the spin lock with interrupts disabled. To workaround the lack of an irqsave variant of refcount_dec_and_lock() they use local_irq_save() at the call site. This causes extra code and creates in some places unneeded long interrupt disabled times. These places need also extra treatment for PREEMPT_RT due to the disconnect of the irq disabling and the lock function. Implement the missing irqsave variant of the function. Signed-off-by:

Anna-Maria Gleixner <anna-maria@linutronix.de> Signed-off-by:

Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r20180612161621.22645-4-bigeasy@linutronix.de [bigeasy: s@atomic_dec_and_lock@refcount_dec_and_lock@g]

include/linux/refcount.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -98,5 +98,7 @@ extern __must_check bool refcount_dec_if_one(refcount_t *r);
		extern __must_check bool refcount_dec_not_one(refcount_t *r);
		extern __must_check bool refcount_dec_and_mutex_lock(refcount_t r, struct mutex lock);
		extern __must_check bool refcount_dec_and_lock(refcount_t r, spinlock_t lock);

		extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
		spinlock_t *lock,
		unsigned long *flags);
		#endif /* _LINUX_REFCOUNT_H */

lib/refcount.c

+28 −0

Original line number	Diff line number	Diff line
		@@ -350,3 +350,31 @@ bool refcount_dec_and_lock(refcount_t r, spinlock_t lock)
		}
		EXPORT_SYMBOL(refcount_dec_and_lock);

		/**
		* refcount_dec_and_lock_irqsave - return holding spinlock with disabled
		* interrupts if able to decrement refcount to 0
		* @r: the refcount
		* @lock: the spinlock to be locked
		* @flags: saved IRQ-flags if the is acquired
		*
		* Same as refcount_dec_and_lock() above except that the spinlock is acquired
		* with disabled interupts.
		*
		* Return: true and hold spinlock if able to decrement refcount to 0, false
		* otherwise
		*/
		bool refcount_dec_and_lock_irqsave(refcount_t r, spinlock_t lock,
		unsigned long *flags)
		{
		if (refcount_dec_not_one(r))
		return false;

		spin_lock_irqsave(lock, *flags);
		if (!refcount_dec_and_test(r)) {
		spin_unlock_irqrestore(lock, *flags);
		return false;
		}

		return true;
		}
		EXPORT_SYMBOL(refcount_dec_and_lock_irqsave);

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