mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-29 07:34:06 +08:00
96567161de
Currently the code tries up to spin_retry times to grab a lock using the cs instruction. The cs instruction has exclusive access to a memory region and therefore invalidates the appropiate cache line of all other cpus. If there is contention on a lock this leads to cache line trashing. This can be avoided if we first check wether a cs instruction is likely to succeed before the instruction gets actually executed. Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
138 lines
2.4 KiB
C
138 lines
2.4 KiB
C
/*
|
|
* arch/s390/lib/spinlock.c
|
|
* Out of line spinlock code.
|
|
*
|
|
* Copyright (C) IBM Corp. 2004, 2006
|
|
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
|
|
*/
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/module.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/init.h>
|
|
#include <asm/io.h>
|
|
|
|
int spin_retry = 1000;
|
|
|
|
/**
|
|
* spin_retry= parameter
|
|
*/
|
|
static int __init spin_retry_setup(char *str)
|
|
{
|
|
spin_retry = simple_strtoul(str, &str, 0);
|
|
return 1;
|
|
}
|
|
__setup("spin_retry=", spin_retry_setup);
|
|
|
|
static inline void
|
|
_diag44(void)
|
|
{
|
|
#ifdef CONFIG_64BIT
|
|
if (MACHINE_HAS_DIAG44)
|
|
#endif
|
|
asm volatile("diag 0,0,0x44");
|
|
}
|
|
|
|
void
|
|
_raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
|
|
{
|
|
int count = spin_retry;
|
|
|
|
while (1) {
|
|
if (count-- <= 0) {
|
|
_diag44();
|
|
count = spin_retry;
|
|
}
|
|
if (__raw_spin_is_locked(lp))
|
|
continue;
|
|
if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
|
|
return;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(_raw_spin_lock_wait);
|
|
|
|
int
|
|
_raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
|
|
{
|
|
int count = spin_retry;
|
|
|
|
while (count-- > 0) {
|
|
if (__raw_spin_is_locked(lp))
|
|
continue;
|
|
if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(_raw_spin_trylock_retry);
|
|
|
|
void
|
|
_raw_read_lock_wait(raw_rwlock_t *rw)
|
|
{
|
|
unsigned int old;
|
|
int count = spin_retry;
|
|
|
|
while (1) {
|
|
if (count-- <= 0) {
|
|
_diag44();
|
|
count = spin_retry;
|
|
}
|
|
if (!__raw_read_can_lock(rw))
|
|
continue;
|
|
old = rw->lock & 0x7fffffffU;
|
|
if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
|
|
return;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(_raw_read_lock_wait);
|
|
|
|
int
|
|
_raw_read_trylock_retry(raw_rwlock_t *rw)
|
|
{
|
|
unsigned int old;
|
|
int count = spin_retry;
|
|
|
|
while (count-- > 0) {
|
|
if (!__raw_read_can_lock(rw))
|
|
continue;
|
|
old = rw->lock & 0x7fffffffU;
|
|
if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(_raw_read_trylock_retry);
|
|
|
|
void
|
|
_raw_write_lock_wait(raw_rwlock_t *rw)
|
|
{
|
|
int count = spin_retry;
|
|
|
|
while (1) {
|
|
if (count-- <= 0) {
|
|
_diag44();
|
|
count = spin_retry;
|
|
}
|
|
if (!__raw_write_can_lock(rw))
|
|
continue;
|
|
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
|
|
return;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(_raw_write_lock_wait);
|
|
|
|
int
|
|
_raw_write_trylock_retry(raw_rwlock_t *rw)
|
|
{
|
|
int count = spin_retry;
|
|
|
|
while (count-- > 0) {
|
|
if (!__raw_write_can_lock(rw))
|
|
continue;
|
|
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(_raw_write_trylock_retry);
|