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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2010-02-26 22:37:40 +0100
committerMartin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com>2010-02-26 22:37:31 +0100
commit59b697874529f5c3cbcaf5816b3d6c584af521e8 (patch)
treec395952c2a0bb9a3027a37a30dd37cc93b1a7c3f /arch/s390
parent8387c736fcbaec17890b8d075ee4f4623518b54a (diff)
[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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/sigp.h40
-rw-r--r--arch/s390/include/asm/smp.h24
-rw-r--r--arch/s390/lib/spinlock.c53
3 files changed, 80 insertions, 37 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
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index cff327f109a8..91754ffb9203 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -43,16 +43,24 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
{
int count = spin_retry;
unsigned int cpu = ~smp_processor_id();
+ unsigned int owner;
while (1) {
- if (count-- <= 0) {
- unsigned int owner = lp->owner_cpu;
- if (owner != 0)
- _raw_yield_cpu(~owner);
- count = spin_retry;
+ owner = lp->owner_cpu;
+ if (!owner || smp_vcpu_scheduled(~owner)) {
+ for (count = spin_retry; count > 0; count--) {
+ if (arch_spin_is_locked(lp))
+ continue;
+ if (_raw_compare_and_swap(&lp->owner_cpu, 0,
+ cpu) == 0)
+ return;
+ }
+ if (MACHINE_IS_LPAR)
+ continue;
}
- if (arch_spin_is_locked(lp))
- continue;
+ owner = lp->owner_cpu;
+ if (owner)
+ _raw_yield_cpu(~owner);
if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
return;
}
@@ -63,17 +71,27 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
{
int count = spin_retry;
unsigned int cpu = ~smp_processor_id();
+ unsigned int owner;
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;
+ owner = lp->owner_cpu;
+ if (!owner || smp_vcpu_scheduled(~owner)) {
+ for (count = spin_retry; count > 0; count--) {
+ if (arch_spin_is_locked(lp))
+ continue;
+ local_irq_disable();
+ if (_raw_compare_and_swap(&lp->owner_cpu, 0,
+ cpu) == 0)
+ return;
+ local_irq_restore(flags);
+ }
+ if (MACHINE_IS_LPAR)
+ continue;
}
- if (arch_spin_is_locked(lp))
- continue;
+ owner = lp->owner_cpu;
+ if (owner)
+ _raw_yield_cpu(~owner);
local_irq_disable();
if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
return;
@@ -100,8 +118,11 @@ EXPORT_SYMBOL(arch_spin_trylock_retry);
void arch_spin_relax(arch_spinlock_t *lock)
{
unsigned int cpu = lock->owner_cpu;
- if (cpu != 0)
- _raw_yield_cpu(~cpu);
+ if (cpu != 0) {
+ if (MACHINE_IS_VM || MACHINE_IS_KVM ||
+ !smp_vcpu_scheduled(~cpu))
+ _raw_yield_cpu(~cpu);
+ }
}
EXPORT_SYMBOL(arch_spin_relax);