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
/*
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* arch/s390/lib/spinlock.c
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* Out of line spinlock code.
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*
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* Copyright (C) IBM Corp. 2004, 2006
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*/
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <asm/io.h>
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int spin_retry = 1000;
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/**
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* spin_retry= parameter
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*/
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static int __init spin_retry_setup(char *str)
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{
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spin_retry = simple_strtoul(str, &str, 0);
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return 1;
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}
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__setup("spin_retry=", spin_retry_setup);
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static inline void
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_diag44(void)
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{
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#ifdef CONFIG_64BIT
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if (MACHINE_HAS_DIAG44)
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#endif
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asm volatile("diag 0,0,0x44");
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}
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void
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_raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
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{
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int count = spin_retry;
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while (1) {
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if (count-- <= 0) {
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_diag44();
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count = spin_retry;
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}
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if (__raw_spin_is_locked(lp))
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continue;
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if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
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return;
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}
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}
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EXPORT_SYMBOL(_raw_spin_lock_wait);
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int
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_raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
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{
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int count = spin_retry;
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while (count-- > 0) {
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if (__raw_spin_is_locked(lp))
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continue;
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if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(_raw_spin_trylock_retry);
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void
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_raw_read_lock_wait(raw_rwlock_t *rw)
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{
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unsigned int old;
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int count = spin_retry;
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while (1) {
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if (count-- <= 0) {
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_diag44();
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count = spin_retry;
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}
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if (!__raw_read_can_lock(rw))
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continue;
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old = rw->lock & 0x7fffffffU;
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if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
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return;
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}
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}
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EXPORT_SYMBOL(_raw_read_lock_wait);
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int
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_raw_read_trylock_retry(raw_rwlock_t *rw)
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{
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unsigned int old;
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int count = spin_retry;
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while (count-- > 0) {
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if (!__raw_read_can_lock(rw))
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continue;
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old = rw->lock & 0x7fffffffU;
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if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(_raw_read_trylock_retry);
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void
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_raw_write_lock_wait(raw_rwlock_t *rw)
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{
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int count = spin_retry;
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while (1) {
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if (count-- <= 0) {
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_diag44();
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count = spin_retry;
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}
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if (!__raw_write_can_lock(rw))
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continue;
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if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
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return;
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}
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}
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EXPORT_SYMBOL(_raw_write_lock_wait);
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int
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_raw_write_trylock_retry(raw_rwlock_t *rw)
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{
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int count = spin_retry;
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while (count-- > 0) {
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if (!__raw_write_can_lock(rw))
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continue;
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if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(_raw_write_trylock_retry);
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