i've split up spinlocking-fixes.patch into 3 parts and reworked them.
This is the first one, against BK-curr:
it fixes the BUILD_LOCK_OPS() bug by introducing the following 3 new
locking primitives:
spin_trylock_test(lock)
read_trylock_test(lock)
write_trylock_test(lock)
this is what is needed by BUILD_LOCK_OPS(): a nonintrusive test to check
whether the real (intrusive) trylock op would succeed or not. Semantics
and naming is completely symmetric to the trylock counterpart. No
changes to exit.c.
build/boot-tested on x86. Architectures that want to support PREEMPT
need to add these definitions.
Ingo
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
--- linux/kernel/spinlock.c.orig
+++ linux/kernel/spinlock.c
@@ -173,8 +173,8 @@ EXPORT_SYMBOL(_write_lock);
* (We do this in a function because inlining it would be excessive.)
*/
-#define BUILD_LOCK_OPS(op, locktype, is_locked_fn) \
-void __lockfunc _##op##_lock(locktype *lock) \
+#define BUILD_LOCK_OPS(op, locktype) \
+void __lockfunc _##op##_lock(locktype##_t *lock) \
{ \
preempt_disable(); \
for (;;) { \
@@ -183,7 +183,7 @@ void __lockfunc _##op##_lock(locktype *l
preempt_enable(); \
if (!(lock)->break_lock) \
(lock)->break_lock = 1; \
- while (is_locked_fn(lock) && (lock)->break_lock) \
+ while (!op##_trylock_test(lock) && (lock)->break_lock) \
cpu_relax(); \
preempt_disable(); \
} \
@@ -191,7 +191,7 @@ void __lockfunc _##op##_lock(locktype *l
\
EXPORT_SYMBOL(_##op##_lock); \
\
-unsigned long __lockfunc _##op##_lock_irqsave(locktype *lock) \
+unsigned long __lockfunc _##op##_lock_irqsave(locktype##_t *lock) \
{ \
unsigned long flags; \
\
@@ -205,7 +205,7 @@ unsigned long __lockfunc _##op##_lock_ir
preempt_enable(); \
if (!(lock)->break_lock) \
(lock)->break_lock = 1; \
- while (is_locked_fn(lock) && (lock)->break_lock) \
+ while (!op##_trylock_test(lock) && (lock)->break_lock) \
cpu_relax(); \
preempt_disable(); \
} \
@@ -214,14 +214,14 @@ unsigned long __lockfunc _##op##_lock_ir
\
EXPORT_SYMBOL(_##op##_lock_irqsave); \
\
-void __lockfunc _##op##_lock_irq(locktype *lock) \
+void __lockfunc _##op##_lock_irq(locktype##_t *lock) \
{ \
_##op##_lock_irqsave(lock); \
} \
\
EXPORT_SYMBOL(_##op##_lock_irq); \
\
-void __lockfunc _##op##_lock_bh(locktype *lock)
\
+void __lockfunc _##op##_lock_bh(locktype##_t *lock) \
{ \
unsigned long flags; \
\
@@ -246,9 +246,9 @@ EXPORT_SYMBOL(_##op##_lock_bh)
* _[spin|read|write]_lock_irqsave()
* _[spin|read|write]_lock_bh()
*/
-BUILD_LOCK_OPS(spin, spinlock_t, spin_is_locked);
-BUILD_LOCK_OPS(read, rwlock_t, rwlock_is_locked);
-BUILD_LOCK_OPS(write, rwlock_t, spin_is_locked);
+BUILD_LOCK_OPS(spin, spinlock);
+BUILD_LOCK_OPS(read, rwlock);
+BUILD_LOCK_OPS(write, rwlock);
#endif /* CONFIG_PREEMPT */
--- linux/include/linux/spinlock.h.orig
+++ linux/include/linux/spinlock.h
@@ -584,4 +584,10 @@ static inline int bit_spin_is_locked(int
#define DEFINE_SPINLOCK(x) spinlock_t x = SPIN_LOCK_UNLOCKED
#define DEFINE_RWLOCK(x) rwlock_t x = RW_LOCK_UNLOCKED
+/**
+ * spin_trylock_test - would spin_trylock() succeed?
+ * @lock: the spinlock in question.
+ */
+#define spin_trylock_test(lock) (!spin_is_locked(lock))
+
#endif /* __LINUX_SPINLOCK_H */
--- linux/include/asm-i386/spinlock.h.orig
+++ linux/include/asm-i386/spinlock.h
@@ -188,6 +188,18 @@ typedef struct {
#define rwlock_is_locked(x) ((x)->lock != RW_LOCK_BIAS)
+/**
+ * read_trylock_test - would read_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+#define read_trylock_test(x) (atomic_read((atomic_t *)&(x)->lock) > 0)
+
+/**
+ * write_trylock_test - would write_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+#define write_trylock_test(x) ((x)->lock == RW_LOCK_BIAS)
+
/*
* On x86, we implement read-write locks as a 32-bit counter
* with the high bit (sign) being the "contended" bit.
-
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