atomic: Add irqsave variant of atomic_dec_and_lock()

[thirdparty/linux.git] / lib / dec_and_lock.c

diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index 347fa7ac2e8a858827415d44725d256d2a9e96a3..9555b68bb774cc3277dca434d19880286d71df0e 100644 (file)
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -33,3 +33,19 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
 }
 
 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);