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s390/spinlock: add compare-and-delay to lock wait loops 

Add the compare-and-delay instruction to the spin-lock and rw-lock
retry loops. A CPU executing the compare-and-delay instruction stops
until the lock value has changed. This is done to make the locking
code for contended locks to behave better in regard to the multi-
hreading facility. A thread of a core executing a compare-and-delay
will allow the other threads of a core to get a larger share of the
core resources.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2015-01-14 17:52:33 +01:00
parent 55b5eb75e7
commit 2c72a44ecd
3 changed files with 66 additions and 7 deletions
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3
arch/s390/include/asm/setup.h
View File

@ -57,6 +57,7 @@ extern void detect_memory_memblock(void);
#define MACHINE_FLAG_TE (1UL << 15)
#define MACHINE_FLAG_TLB_LC (1UL << 17)
#define MACHINE_FLAG_VX (1UL << 18)
#define MACHINE_FLAG_CAD (1UL << 19)
#define MACHINE_IS_VM (S390_lowcore.machine_flags & MACHINE_FLAG_VM)
#define MACHINE_IS_KVM (S390_lowcore.machine_flags & MACHINE_FLAG_KVM)
@ -80,6 +81,7 @@ extern void detect_memory_memblock(void);
#define MACHINE_HAS_TE (0)
#define MACHINE_HAS_TLB_LC (0)
#define MACHINE_HAS_VX (0)
#define MACHINE_HAS_CAD (0)
#else /* CONFIG_64BIT */
#define MACHINE_HAS_IEEE (1)
#define MACHINE_HAS_CSP (1)
@ -93,6 +95,7 @@ extern void detect_memory_memblock(void);
#define MACHINE_HAS_TE (S390_lowcore.machine_flags & MACHINE_FLAG_TE)
#define MACHINE_HAS_TLB_LC (S390_lowcore.machine_flags & MACHINE_FLAG_TLB_LC)
#define MACHINE_HAS_VX (S390_lowcore.machine_flags & MACHINE_FLAG_VX)
#define MACHINE_HAS_CAD (S390_lowcore.machine_flags & MACHINE_FLAG_CAD)
#endif /* CONFIG_64BIT */
/*

18
arch/s390/kernel/early.c
View File

@ -393,9 +393,27 @@ static __init void detect_machine_facilities(void)
S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC;
if (test_facility(129))
S390_lowcore.machine_flags |= MACHINE_FLAG_VX;
if (test_facility(128))
S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
#endif
}
static int __init nocad_setup(char *str)
{
S390_lowcore.machine_flags &= ~MACHINE_FLAG_CAD;
return 0;
}
early_param("nocad", nocad_setup);
static int __init cad_init(void)
{
if (MACHINE_HAS_CAD)
/* Enable problem state CAD. */
__ctl_set_bit(2, 3);
return 0;
}
early_initcall(cad_init);
static __init void rescue_initrd(void)
{
#ifdef CONFIG_BLK_DEV_INITRD

52
arch/s390/lib/spinlock.c
View File

@ -12,7 +12,15 @@
#include <linux/smp.h>
#include <asm/io.h>
int spin_retry = 1000;
int spin_retry = -1;
static int __init spin_retry_init(void)
{
if (spin_retry < 0)
spin_retry = MACHINE_HAS_CAD ? 10 : 1000;
return 0;
}
early_initcall(spin_retry_init);
/**
* spin_retry= parameter
@ -24,6 +32,11 @@ static int __init spin_retry_setup(char *str)
}
__setup("spin_retry=", spin_retry_setup);
static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
{
asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
}
void arch_spin_lock_wait(arch_spinlock_t *lp)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
@ -46,6 +59,8 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
/* Loop for a while on the lock value. */
count = spin_retry;
do {
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&lp->lock, owner);
owner = ACCESS_ONCE(lp->lock);
} while (owner && count-- > 0);
if (!owner)
@ -84,6 +99,8 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
/* Loop for a while on the lock value. */
count = spin_retry;
do {
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&lp->lock, owner);
owner = ACCESS_ONCE(lp->lock);
} while (owner && count-- > 0);
if (!owner)
@ -100,11 +117,19 @@ EXPORT_SYMBOL(arch_spin_lock_wait_flags);
int arch_spin_trylock_retry(arch_spinlock_t *lp)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
unsigned int owner;
int count;
for (count = spin_retry; count > 0; count--)
if (arch_spin_trylock_once(lp))
return 1;
for (count = spin_retry; count > 0; count--) {
owner = ACCESS_ONCE(lp->lock);
/* Try to get the lock if it is free. */
if (!owner) {
if (_raw_compare_and_swap(&lp->lock, 0, cpu))
return 1;
} else if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&lp->lock, owner);
}
return 0;
}
EXPORT_SYMBOL(arch_spin_trylock_retry);
@ -126,8 +151,11 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
}
old = ACCESS_ONCE(rw->lock);
owner = ACCESS_ONCE(rw->owner);
if ((int) old < 0)
if ((int) old < 0) {
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&rw->lock, old);
continue;
}
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
return;
}
@ -141,8 +169,11 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw)
while (count-- > 0) {
old = ACCESS_ONCE(rw->lock);
if ((int) old < 0)
if ((int) old < 0) {
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&rw->lock, old);
continue;
}
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
return 1;
}
@ -173,6 +204,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
}
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
break;
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&rw->lock, old);
}
}
EXPORT_SYMBOL(_raw_write_lock_wait);
@ -201,6 +234,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
smp_rmb();
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
break;
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&rw->lock, old);
}
}
EXPORT_SYMBOL(_raw_write_lock_wait);
@ -214,8 +249,11 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw)
while (count-- > 0) {
old = ACCESS_ONCE(rw->lock);
if (old)
if (old) {
if (MACHINE_HAS_CAD)
_raw_compare_and_delay(&rw->lock, old);
continue;
}
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
return 1;
}