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SubjectRe: [patch 1/3] spinlock fix #1, *_can_lock() primitives

* Linus Torvalds <torvalds@osdl.org> wrote:

> I can do ppc64 myself, can others fix the other architectures (Ingo,
> shouldn't the UP case have the read/write_can_lock() cases too? And
> wouldn't you agree that it makes more sense to have the rwlock test
> variants in asm/rwlock.h?):

You are right about UP, and the patch below adds the UP variants. It's
analogous to the existing wrapping concept that UP 'spinlocks' are
always unlocked on UP. (spin_can_lock() is already properly defined on
UP too.)

Ingo

Signed-off-by: Ingo Molnar <mingo@elte.hu>

--- linux/include/linux/spinlock.h.orig
+++ linux/include/linux/spinlock.h
@@ -228,6 +228,9 @@ typedef struct {

#define rwlock_yield(lock) (void)(lock)

+#define read_can_lock(lock) (((void)(lock), 1))
+#define write_can_lock(lock) (((void)(lock), 1))
+
#define _spin_trylock(lock) ({preempt_disable(); _raw_spin_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})

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