[PATCH] s390: do local_irq_restore while spinning in spin_lock_irqsave

[Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>]

Hi

In s390's spin_lock_irqsave, interrupts remain disabled while spinning.
In other architectures like x86 and powerpc, interrupts are re-enabled 
while spinning
if IRQ is not masked before spin_lock_irqsave is called.

The following patch re-enables interrupts through local_irq_restore while 
spinning
for a lock acquisition. This can improve system response.

Comments?

Thanks.

Signed-off-by :Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>

diff -Nrup linux-2.6.24-rc8.org/arch/s390/lib/spinlock.c 
linux-2.6.24-rc8/arch/s390/lib/spinlock.c
--- linux-2.6.24-rc8.org/arch/s390/lib/spinlock.c	2007-10-10 
05:31:38.000000000 +0900
+++ linux-2.6.24-rc8/arch/s390/lib/spinlock.c	2008-01-21 19:20:43.000000000 +0900
@@ -61,6 +61,32 @@ void _raw_spin_lock_wait(raw_spinlock_t
 }
 EXPORT_SYMBOL(_raw_spin_lock_wait);

+void _raw_spin_lock_wait_flags(raw_spinlock_t *lp,
+			       unsigned int pc, unsigned long flags)
+{
+	int count = spin_retry;
+	unsigned int cpu = ~smp_processor_id();
+
+	local_irq_restore(flags);
+	while (1) {
+		if (count-- <= 0) {
+			unsigned int owner = lp->owner_cpu;
+			if (owner != 0)
+				_raw_yield_cpu(~owner);
+			count = spin_retry;
+		}
+		if (__raw_spin_is_locked(lp))
+			continue;
+		local_irq_disable();
+		if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0) {
+			lp->owner_pc = pc;
+			return;
+		}
+		local_irq_restore(flags);
+	}
+}
+EXPORT_SYMBOL(_raw_spin_lock_wait_flags);
+
 int _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
 {
 	unsigned int cpu = ~smp_processor_id();
diff -Nrup linux-2.6.24-rc8.org/include/asm-s390/spinlock.h 
linux-2.6.24-rc8/include/asm-s390/spinlock.h
--- linux-2.6.24-rc8.org/include/asm-s390/spinlock.h	2007-10-10 
05:31:38.000000000 +0900
+++ linux-2.6.24-rc8/include/asm-s390/spinlock.h	2008-01-21 
19:20:43.000000000 +0900
@@ -53,12 +53,13 @@ _raw_compare_and_swap(volatile unsigned
  */

 #define __raw_spin_is_locked(x) ((x)->owner_cpu != 0)
-#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
 #define __raw_spin_unlock_wait(lock) \
 	do { while (__raw_spin_is_locked(lock)) \
 		 _raw_spin_relax(lock); } while (0)

 extern void _raw_spin_lock_wait(raw_spinlock_t *, unsigned int pc);
+extern void _raw_spin_lock_wait_flags(raw_spinlock_t *,
+				      unsigned int pc, unsigned long flags);
 extern int _raw_spin_trylock_retry(raw_spinlock_t *, unsigned int pc);
 extern void _raw_spin_relax(raw_spinlock_t *lock);

@@ -75,6 +76,19 @@ static inline void __raw_spin_lock(raw_s
 	_raw_spin_lock_wait(lp, pc);
 }

+static inline void __raw_spin_lock_flags(raw_spinlock_t *lp, unsigned long 
flags)
+{
+	unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
+	int old;
+
+	old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
+	if (likely(old == 0)) {
+		lp->owner_pc = pc;
+		return;
+	}
+	_raw_spin_lock_wait_flags(lp, pc, flags);
+}
+
 static inline int __raw_spin_trylock(raw_spinlock_t *lp)
 {
 	unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);


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