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SubjectRe: [PATCH] i386 spinlocks should use the full 32 bits, not only 8 bits

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

>
>
> On Fri, 21 Oct 2005, Ingo Molnar wrote:
> >
> > the unlock is simple even in the preemption case
>
> No it's not. It needs to decrement the preemption counter and test it.

arghhh. Right you are. I even had the proper solution coded up initially
(i had || defined(CONFIG_PREEMPT)) but dropped it due to fatal brain
error. Been hacking on way too much ktimer code today ... Hopefully
better patch attached. Booted on SMP+PREEMPT x86. But i'd really advise
you against taking patches from me tonight :-|
Ingo

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

include/linux/spinlock.h | 15 ++++++++++++---
1 files changed, 12 insertions(+), 3 deletions(-)
Index: linux/include/linux/spinlock.h
===================================================================
--- linux.orig/include/linux/spinlock.h
+++ linux/include/linux/spinlock.h
@@ -171,9 +171,18 @@ extern int __lockfunc generic__raw_read_
#define write_lock_irq(lock) _write_lock_irq(lock)
#define write_lock_bh(lock) _write_lock_bh(lock)

-#define spin_unlock(lock) _spin_unlock(lock)
-#define write_unlock(lock) _write_unlock(lock)
-#define read_unlock(lock) _read_unlock(lock)
+/*
+ * We inline the unlock functions in the nondebug case:
+ */
+#if defined(CONFIG_DEBUG_SPINLOCK) || defined(CONFIG_PREEMPT)
+# define spin_unlock(lock) _spin_unlock(lock)
+# define read_unlock(lock) _read_unlock(lock)
+# define write_unlock(lock) _write_unlock(lock)
+#else
+# define spin_unlock(lock) __raw_spin_unlock(&(lock)->raw_lock)
+# define read_unlock(lock) __raw_read_unlock(&(lock)->raw_lock)
+# define write_unlock(lock) __raw_write_unlock(&(lock)->raw_lock)
+#endif

#define spin_unlock_irqrestore(lock, flags) \
_spin_unlock_irqrestore(lock, flags)
-
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