mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-11-01 08:58:07 +00:00
ccfbb5bed4
There are in-tree users of atomic_dec_and_lock() which must acquire the spin lock with interrupts disabled. To workaround the lack of an irqsave variant of atomic_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/r20180612161621.22645-3-bigeasy@linutronix.de
51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/export.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/atomic.h>
|
|
|
|
/*
|
|
* This is an implementation of the notion of "decrement a
|
|
* reference count, and return locked if it decremented to zero".
|
|
*
|
|
* NOTE NOTE NOTE! This is _not_ equivalent to
|
|
*
|
|
* if (atomic_dec_and_test(&atomic)) {
|
|
* spin_lock(&lock);
|
|
* return 1;
|
|
* }
|
|
* return 0;
|
|
*
|
|
* because the spin-lock and the decrement must be
|
|
* "atomic".
|
|
*/
|
|
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
|
|
{
|
|
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
|
|
if (atomic_add_unless(atomic, -1, 1))
|
|
return 0;
|
|
|
|
/* Otherwise do it the slow way */
|
|
spin_lock(lock);
|
|
if (atomic_dec_and_test(atomic))
|
|
return 1;
|
|
spin_unlock(lock);
|
|
return 0;
|
|
}
|
|
|
|
EXPORT_SYMBOL(_atomic_dec_and_lock);
|
|
|
|
int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
|
|
unsigned long *flags)
|
|
{
|
|
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
|
|
if (atomic_add_unless(atomic, -1, 1))
|
|
return 0;
|
|
|
|
/* Otherwise do it the slow way */
|
|
spin_lock_irqsave(lock, *flags);
|
|
if (atomic_dec_and_test(atomic))
|
|
return 1;
|
|
spin_unlock_irqrestore(lock, *flags);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave);
|