[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();