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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-03-25 03:53:42 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-03-25 03:53:42 -0300
commit03dd4cb26d967f9588437b0fc9cc0e8353322bb7 (patch)
treefa581f6dc1c0596391690d1f67eceef3af8246dc /arch/s390/lib/spinlock.c
parentd4e493caf788ef44982e131ff9c786546904d934 (diff)
Linux-libre 4.5-gnu
Diffstat (limited to 'arch/s390/lib/spinlock.c')
-rw-r--r--arch/s390/lib/spinlock.c45
1 files changed, 32 insertions, 13 deletions
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 427aa44b3..d4549c964 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -37,12 +37,22 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
}
+static inline int cpu_is_preempted(int cpu)
+{
+ if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
+ return 0;
+ if (smp_vcpu_scheduled(cpu))
+ return 0;
+ return 1;
+}
+
void arch_spin_lock_wait(arch_spinlock_t *lp)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
unsigned int owner;
- int count;
+ int count, first_diag;
+ first_diag = 1;
while (1) {
owner = ACCESS_ONCE(lp->lock);
/* Try to get the lock if it is free. */
@@ -51,9 +61,10 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
return;
continue;
}
- /* Check if the lock owner is running. */
- if (!smp_vcpu_scheduled(~owner)) {
+ /* First iteration: check if the lock owner is running. */
+ if (first_diag && cpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
+ first_diag = 0;
continue;
}
/* Loop for a while on the lock value. */
@@ -67,10 +78,13 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
continue;
/*
* For multiple layers of hypervisors, e.g. z/VM + LPAR
- * yield the CPU if the lock is still unavailable.
+ * yield the CPU unconditionally. For LPAR rely on the
+ * sense running status.
*/
- if (!MACHINE_IS_LPAR)
+ if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
+ first_diag = 0;
+ }
}
}
EXPORT_SYMBOL(arch_spin_lock_wait);
@@ -79,9 +93,10 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
unsigned int owner;
- int count;
+ int count, first_diag;
local_irq_restore(flags);
+ first_diag = 1;
while (1) {
owner = ACCESS_ONCE(lp->lock);
/* Try to get the lock if it is free. */
@@ -92,8 +107,9 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
local_irq_restore(flags);
}
/* Check if the lock owner is running. */
- if (!smp_vcpu_scheduled(~owner)) {
+ if (first_diag && cpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
+ first_diag = 0;
continue;
}
/* Loop for a while on the lock value. */
@@ -107,10 +123,13 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
continue;
/*
* For multiple layers of hypervisors, e.g. z/VM + LPAR
- * yield the CPU if the lock is still unavailable.
+ * yield the CPU unconditionally. For LPAR rely on the
+ * sense running status.
*/
- if (!MACHINE_IS_LPAR)
+ if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
+ first_diag = 0;
+ }
}
}
EXPORT_SYMBOL(arch_spin_lock_wait_flags);
@@ -145,7 +164,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && !smp_vcpu_scheduled(~owner))
+ if (owner && cpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -191,7 +210,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && !smp_vcpu_scheduled(~owner))
+ if (owner && cpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -221,7 +240,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && !smp_vcpu_scheduled(~owner))
+ if (owner && cpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -265,7 +284,7 @@ void arch_lock_relax(unsigned int cpu)
{
if (!cpu)
return;
- if (MACHINE_IS_LPAR && smp_vcpu_scheduled(~cpu))
+ if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
return;
smp_yield_cpu(~cpu);
}