[S390] spinlock: check virtual cpu running status
This patch introduces a new function that checks the running status
of a cpu in a hypervisor. This status is not virtualized, so the check
is only correct if running in an LPAR. On acquiring a spinlock, if the
cpu holding the lock is scheduled by the hypervisor, we do a busy wait
on the lock. If it is not scheduled, we yield over to that cpu.
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h
index c2d0e63..edc03cb 100644
--- a/arch/s390/include/asm/smp.h
+++ b/arch/s390/include/asm/smp.h
@@ -36,6 +36,28 @@
int from, int to);
extern void smp_restart_cpu(void);
+/*
+ * returns 1 if (virtual) cpu is scheduled
+ * returns 0 otherwise
+ */
+static inline int smp_vcpu_scheduled(int cpu)
+{
+ u32 status;
+
+ switch (sigp_ps(&status, 0, cpu, sigp_sense_running)) {
+ case sigp_status_stored:
+ /* Check for running status */
+ if (status & 0x400)
+ return 0;
+ break;
+ case sigp_not_operational:
+ return 0;
+ default:
+ break;
+ }
+ return 1;
+}
+
#else /* CONFIG_SMP */
static inline void smp_switch_to_ipl_cpu(void (*func)(void *), void *data)
@@ -43,6 +65,8 @@
func(data);
}
+#define smp_vcpu_scheduled (1)
+
#endif /* CONFIG_SMP */
#ifdef CONFIG_HOTPLUG_CPU