diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/ia64/lib/dec_and_lock.c |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'arch/ia64/lib/dec_and_lock.c')
-rw-r--r-- | arch/ia64/lib/dec_and_lock.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/arch/ia64/lib/dec_and_lock.c b/arch/ia64/lib/dec_and_lock.c new file mode 100644 index 00000000000..c7ce92f968f --- /dev/null +++ b/arch/ia64/lib/dec_and_lock.c @@ -0,0 +1,42 @@ +/* + * Copyright (C) 2003 Jerome Marchand, Bull S.A. + * Cleaned up by David Mosberger-Tang <davidm@hpl.hp.com> + * + * This file is released under the GPLv2, or at your option any later version. + * + * ia64 version of "atomic_dec_and_lock()" using the atomic "cmpxchg" instruction. This + * code is an adaptation of the x86 version of "atomic_dec_and_lock()". + */ + +#include <linux/compiler.h> +#include <linux/module.h> +#include <linux/spinlock.h> +#include <asm/atomic.h> + +/* + * Decrement REFCOUNT and if the count reaches zero, acquire the spinlock. Both of these + * operations have to be done atomically, so that the count doesn't drop to zero without + * acquiring the spinlock first. + */ +int +_atomic_dec_and_lock (atomic_t *refcount, spinlock_t *lock) +{ + int old, new; + + do { + old = atomic_read(refcount); + new = old - 1; + + if (unlikely (old == 1)) { + /* oops, we may be decrementing to zero, do it the slow way... */ + spin_lock(lock); + if (atomic_dec_and_test(refcount)) + return 1; + spin_unlock(lock); + return 0; + } + } while (cmpxchg(&refcount->counter, old, new) != old); + return 0; +} + +EXPORT_SYMBOL(_atomic_dec_and_lock); |