Subject: Spinlocks: Factor our GENERIC_LOCKBREAK in order to avoid spin with irqs disabled
The nice spinlock functions that enable interrupts while spinning are only
usable if GENERIC_LOCKBREAK is set (and we do not debug locks but lock
debugging would not be used for a production configuration).
Factor out the dependencies on the ->lock_break field from the nice functions
into a set of BREAKLOCK macros (cannot be functions since the type of the lock
variable varies).
The nice spinlock function can then also be used if !GENERIC_LOCKBREAK
Signed-off-by: Christoph Lameter <clameter@sgi.com>
---
kernel/spinlock.c | 40 ++++++++++++++++++++++++++++++----------
1 file changed, 30 insertions(+), 10 deletions(-)
Index: linux-2.6/kernel/spinlock.c
===================================================================
--- linux-2.6.orig/kernel/spinlock.c 2008-05-07 11:19:31.000000000 -0700
+++ linux-2.6/kernel/spinlock.c 2008-05-07 11:40:56.000000000 -0700
@@ -65,7 +65,7 @@ EXPORT_SYMBOL(_write_trylock);
* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
* not re-enabled during lock-acquire (which the preempt-spin-ops do):
*/
-#if !defined(CONFIG_GENERIC_LOCKBREAK) || defined(CONFIG_DEBUG_LOCK_ALLOC)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __lockfunc _read_lock(rwlock_t *lock)
{
@@ -192,7 +192,7 @@ void __lockfunc _write_lock(rwlock_t *lo
EXPORT_SYMBOL(_write_lock);
-#else /* CONFIG_PREEMPT: */
+#else /* CONFIG_DEBUG_LOCK_ALLOC: */
/*
* This could be a long-held lock. We both prepare to spin for a long
@@ -201,6 +201,28 @@ EXPORT_SYMBOL(_write_lock);
*
* (We do this in a function because inlining it would be excessive.)
*/
+#ifdef CONFIG_GENERIC_LOCKBREAK
+
+#define BREAKLOCK(lock) (lock)->break_lock
+
+#define BREAKLOCK_ENABLE(lock) \
+do { \
+ if (!(lock)->break_lock) \
+ (lock)->break_lock = 1; \
+} while (0)
+
+#define BREAKLOCK_DISABLE(lock) \
+do { \
+ (lock)->break_lock = 0; \
+} while (0)
+
+#else
+
+#define BREAKLOCK(lock) 0
+#define BREAKLOCK_ENABLE(lock) do { } while (0)
+#define BREAKLOCK_DISABLE(lock) do { } while (0)
+
+#endif
#define BUILD_LOCK_OPS(op, locktype) \
void __lockfunc _##op##_lock(locktype##_t *lock) \
@@ -211,12 +233,11 @@ void __lockfunc _##op##_lock(locktype##_
break; \
preempt_enable(); \
\
- if (!(lock)->break_lock) \
- (lock)->break_lock = 1; \
- while (!op##_can_lock(lock) && (lock)->break_lock) \
+ BREAKLOCK_ENABLE(lock); \
+ while (!op##_can_lock(lock) && BREAKLOCK(lock)) \
_raw_##op##_relax(&lock->raw_lock); \
} \
- (lock)->break_lock = 0; \
+ BREAKLOCK_DISABLE(lock); \
} \
\
EXPORT_SYMBOL(_##op##_lock); \
@@ -233,12 +254,11 @@ unsigned long __lockfunc _##op##_lock_ir
local_irq_restore(flags); \
preempt_enable(); \
\
- if (!(lock)->break_lock) \
- (lock)->break_lock = 1; \
- while (!op##_can_lock(lock) && (lock)->break_lock) \
+ BREAKLOCK_ENABLE(lock); \
+ while (!op##_can_lock(lock) && BREAKLOCK(lock)) \
_raw_##op##_relax(&lock->raw_lock); \
} \
- (lock)->break_lock = 0; \
+ BREAKLOCK_DISABLE(lock); \
return flags; \
} \
\
--
