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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2014-09-19 14:29:31 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2014-09-25 10:52:05 +0200
commitd59b93da5e572703e1a7311c13dd3472a4e56e30 (patch)
tree4c75073780f54bc9785433256eee3d6d70eaf868 /arch/s390/lib/spinlock.c
parents390/zcrypt: Fixed possible race condition in zcrypt module handling (diff)
downloadlinux-d59b93da5e572703e1a7311c13dd3472a4e56e30.tar.xz
linux-d59b93da5e572703e1a7311c13dd3472a4e56e30.zip
s390/rwlock: use directed yield for write-locked rwlocks
Add an owner field to the arch_rwlock_t to be able to pass the timeslice of a virtual CPU with diagnose 0x9c to the lock owner in case the rwlock is write-locked. The undirected yield in case the rwlock is acquired writable but the lock is read-locked is removed. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/lib/spinlock.c')
-rw-r--r--arch/s390/lib/spinlock.c49
1 files changed, 30 insertions, 19 deletions
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 5b0e445bc3f3..5f63ac5783cb 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -98,17 +98,6 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
}
EXPORT_SYMBOL(arch_spin_lock_wait_flags);
-void arch_spin_relax(arch_spinlock_t *lp)
-{
- unsigned int cpu = lp->lock;
- if (cpu != 0) {
- if (MACHINE_IS_VM || MACHINE_IS_KVM ||
- !smp_vcpu_scheduled(~cpu))
- smp_yield_cpu(~cpu);
- }
-}
-EXPORT_SYMBOL(arch_spin_relax);
-
int arch_spin_trylock_retry(arch_spinlock_t *lp)
{
int count;
@@ -122,15 +111,18 @@ EXPORT_SYMBOL(arch_spin_trylock_retry);
void _raw_read_lock_wait(arch_rwlock_t *rw)
{
- unsigned int old;
+ unsigned int owner, old;
int count = spin_retry;
+ owner = 0;
while (1) {
if (count-- <= 0) {
- smp_yield();
+ if (owner && !smp_vcpu_scheduled(~owner))
+ smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
+ owner = ACCESS_ONCE(rw->owner);
if ((int) old < 0)
continue;
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
@@ -141,16 +133,19 @@ EXPORT_SYMBOL(_raw_read_lock_wait);
void _raw_read_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags)
{
- unsigned int old;
+ unsigned int owner, old;
int count = spin_retry;
local_irq_restore(flags);
+ owner = 0;
while (1) {
if (count-- <= 0) {
- smp_yield();
+ if (owner && !smp_vcpu_scheduled(~owner))
+ smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
+ owner = ACCESS_ONCE(rw->owner);
if ((int) old < 0)
continue;
local_irq_disable();
@@ -179,15 +174,18 @@ EXPORT_SYMBOL(_raw_read_trylock_retry);
void _raw_write_lock_wait(arch_rwlock_t *rw)
{
- unsigned int old;
+ unsigned int owner, old;
int count = spin_retry;
+ owner = 0;
while (1) {
if (count-- <= 0) {
- smp_yield();
+ if (owner && !smp_vcpu_scheduled(~owner))
+ smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
+ owner = ACCESS_ONCE(rw->owner);
if (old)
continue;
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
@@ -198,16 +196,19 @@ EXPORT_SYMBOL(_raw_write_lock_wait);
void _raw_write_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags)
{
- unsigned int old;
+ unsigned int owner, old;
int count = spin_retry;
local_irq_restore(flags);
+ owner = 0;
while (1) {
if (count-- <= 0) {
- smp_yield();
+ if (owner && !smp_vcpu_scheduled(~owner))
+ smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
+ owner = ACCESS_ONCE(rw->owner);
if (old)
continue;
local_irq_disable();
@@ -233,3 +234,13 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw)
return 0;
}
EXPORT_SYMBOL(_raw_write_trylock_retry);
+
+void arch_lock_relax(unsigned int cpu)
+{
+ if (!cpu)
+ return;
+ if (MACHINE_IS_LPAR && smp_vcpu_scheduled(~cpu))
+ return;
+ smp_yield_cpu(~cpu);
+}
+EXPORT_SYMBOL(arch_lock_relax);