[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>

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 59c56c3d72d0..e41f4008afc5 100644
--- 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();