[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>

2 files changed, 43 insertions, 21 deletions

diff --git a/arch/s390/include/asm/sigp.h b/arch/s390/include/asm/sigp.h
index 8aa46ce4229c..e3bffd4e2d66 100644
--- a/arch/s390/include/asm/sigp.h
+++ b/arch/s390/include/asm/sigp.h
@@ -25,29 +25,28 @@ static inline int cpu_logical_map(int cpu)
 }
 
 enum {
-        sigp_unassigned=0x0,
-        sigp_sense,
-        sigp_external_call,
-        sigp_emergency_signal,
-        sigp_start,
-        sigp_stop,
-        sigp_restart,
-        sigp_unassigned1,
-        sigp_unassigned2,
-        sigp_stop_and_store_status,
-        sigp_unassigned3,
-        sigp_initial_cpu_reset,
-        sigp_cpu_reset,
-        sigp_set_prefix,
-        sigp_store_status_at_address,
-        sigp_store_extended_status_at_address
+        sigp_sense = 1,
+        sigp_external_call = 2,
+        sigp_emergency_signal = 3,
+        sigp_start = 4,
+        sigp_stop = 5,
+        sigp_restart = 6,
+        sigp_stop_and_store_status = 9,
+        sigp_initial_cpu_reset = 11,
+        sigp_cpu_reset = 12,
+        sigp_set_prefix = 13,
+        sigp_store_status_at_address = 14,
+        sigp_store_extended_status_at_address = 15,
+        sigp_set_architecture = 18,
+        sigp_conditional_emergency_signal = 19,
+        sigp_sense_running = 21,
 };
 
 enum {
-        sigp_order_code_accepted=0,
-        sigp_status_stored,
-        sigp_busy,
-        sigp_not_operational
+        sigp_order_code_accepted = 0,
+        sigp_status_stored = 1,
+        sigp_busy = 2,
+        sigp_not_operational = 3,
 };
 
 /*
@@ -57,7 +56,6 @@ enum {
         ec_schedule = 0,
         ec_call_function,
         ec_call_function_single,
-        ec_bit_last
 };
 
 /*
diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h
index c2d0e638f892..edc03cb9cd79 100644
--- a/arch/s390/include/asm/smp.h
+++ b/arch/s390/include/asm/smp.h
@@ -36,6 +36,28 @@ extern void smp_switch_to_cpu(void (*)(void *), void *, unsigned long sp,
                               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 @@ static inline void smp_switch_to_ipl_cpu(void (*func)(void *), void *data)
         func(data);
 }
 
+#define smp_vcpu_scheduled      (1)
+
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_HOTPLUG_CPU