[S390] do local_irq_restore while spinning in spin_lock_irqsave.

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.

[heiko.carstens@de.ibm.com: removed saving of pc]

Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 59c56c3..e41f400 100644 (file)
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -59,6 +59,29 @@ void _raw_spin_lock_wait(raw_spinlock_t *lp)
 }
 EXPORT_SYMBOL(_raw_spin_lock_wait);
 
+void _raw_spin_lock_wait_flags(raw_spinlock_t *lp, 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)
+                       return;
+               local_irq_restore(flags);
+       }
+}
+EXPORT_SYMBOL(_raw_spin_lock_wait_flags);
+
 int _raw_spin_trylock_retry(raw_spinlock_t *lp)
 {
        unsigned int cpu = ~smp_processor_id();

diff --git a/include/asm-s390/spinlock.h b/include/asm-s390/spinlock.h
index c1d6e7e..df84ae9 100644 (file)
--- a/include/asm-s390/spinlock.h
+++ b/include/asm-s390/spinlock.h
@@ -53,12 +53,12 @@ _raw_compare_and_swap(volatile unsigned int *lock,
  */
 
 #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 *);
+extern void _raw_spin_lock_wait_flags(raw_spinlock_t *, unsigned long flags);
 extern int _raw_spin_trylock_retry(raw_spinlock_t *);
 extern void _raw_spin_relax(raw_spinlock_t *lock);
 
@@ -72,6 +72,17 @@ static inline void __raw_spin_lock(raw_spinlock_t *lp)
        _raw_spin_lock_wait(lp);
 }
 
+static inline void __raw_spin_lock_flags(raw_spinlock_t *lp,
+                                        unsigned long flags)
+{
+       int old;
+
+       old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
+       if (likely(old == 0))
+               return;
+       _raw_spin_lock_wait_flags(lp, flags);
+}
+
 static inline int __raw_spin_trylock(raw_spinlock_t *lp)
 {
        int old;