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authorAnna-Maria Gleixner <anna-maria@linutronix.de>2018-06-12 18:16:21 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-06-12 23:33:25 +0200
commit7ea959c45769612aa92557fb6464679f5fec7d9e (patch)
tree59727b6ac6c32a2addb41cab2c875ab7caee1b75 /lib
parentccfbb5bed407053b27492a9adc06064d949a9aa6 (diff)
downloadlinux-7ea959c45769612aa92557fb6464679f5fec7d9e.tar.bz2
locking/refcounts: Implement refcount_dec_and_lock_irqsave()
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]
Diffstat (limited to 'lib')
-rw-r--r--lib/refcount.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/lib/refcount.c b/lib/refcount.c
index 0eb48353abe3..d3b81cefce91 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -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);