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[PATCH] s390: spin lock retry

Browse source 
Split spin lock and r/w lock implementation into a single try which is done
inline and an out of line function that repeatedly tries to get the lock
before doing the cpu_relax().  Add a system control to set the number of
retries before a cpu is yielded.

The reason for the spin lock retry is that the diagnose 0x44 that is used to
give up the virtual cpu is quite expensive.  For spin locks that are held only
for a short period of time the costs of the diagnoses outweights the savings
for spin locks that are held for a longer timer.  The default retry count is
1000.

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>
This commit is contained in:
Martin Schwidefsky 2005-07-27 11:44:57 -07:00 committed by Linus Torvalds
parent 8449d003f3
commit 951f22d5b1
9 changed files with 228 additions and 188 deletions
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3
arch/s390/kernel/head64.S
View file

@ -658,10 +658,8 @@ startup:basr %r13,0 # get base
#
la %r1,0f-.LPG1(%r13) # set program check address
stg %r1,__LC_PGM_NEW_PSW+8
mvc __LC_DIAG44_OPCODE(8),.Lnop-.LPG1(%r13)
diag 0,0,0x44 # test diag 0x44
oi 7(%r12),32 # set diag44 flag
mvc __LC_DIAG44_OPCODE(8),.Ldiag44-.LPG1(%r13)
0:
#
@ -702,7 +700,6 @@ startup:basr %r13,0 # get base
.L4malign:.quad 0xffffffffffc00000
.Lscan2g:.quad 0x80000000 + 0x20000 - 8 # 2GB + 128K - 8
.Lnop: .long 0x07000700
.Ldiag44:.long 0x83000044
.org PARMAREA-64
.Lduct: .long 0,0,0,0,0,0,0,0

6
arch/s390/kernel/setup.c
View file

@ -431,12 +431,6 @@ setup_lowcore(void)
ctl_set_bit(14, 29);
}
#endif
#ifdef CONFIG_ARCH_S390X
if (MACHINE_HAS_DIAG44)
lc->diag44_opcode = 0x83000044;
else
lc->diag44_opcode = 0x07000700;
#endif /* CONFIG_ARCH_S390X */
set_prefix((u32)(unsigned long) lc);
}

4
arch/s390/lib/Makefile
View file

@ -5,5 +5,5 @@
EXTRA_AFLAGS := -traditional
lib-y += delay.o string.o
lib-$(CONFIG_ARCH_S390_31) += uaccess.o
lib-$(CONFIG_ARCH_S390X) += uaccess64.o
lib-$(CONFIG_ARCH_S390_31) += uaccess.o spinlock.o
lib-$(CONFIG_ARCH_S390X) += uaccess64.o spinlock.o

133
arch/s390/lib/spinlock.c Normal file
View file

@ -0,0 +1,133 @@
/*
* arch/s390/lib/spinlock.c
* Out of line spinlock code.
*
* S390 version
* Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
* 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>
atomic_t spin_retry_counter;
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 __s390x__
if (MACHINE_HAS_DIAG44)
#endif
asm volatile("diag 0,0,0x44");
}
void
_raw_spin_lock_wait(spinlock_t *lp, unsigned int pc)
{
int count = spin_retry;
while (1) {
if (count-- <= 0) {
_diag44();
count = spin_retry;
}
atomic_inc(&spin_retry_counter);
if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
return;
}
}
EXPORT_SYMBOL(_raw_spin_lock_wait);
int
_raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc)
{
int count = spin_retry;
while (count-- > 0) {
atomic_inc(&spin_retry_counter);
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(rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;
while (1) {
if (count-- <= 0) {
_diag44();
count = spin_retry;
}
atomic_inc(&spin_retry_counter);
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(rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;
while (count-- > 0) {
atomic_inc(&spin_retry_counter);
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(rwlock_t *rw)
{
int count = spin_retry;
while (1) {
if (count-- <= 0) {
_diag44();
count = spin_retry;
}
atomic_inc(&spin_retry_counter);
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
return;
}
}
EXPORT_SYMBOL(_raw_write_lock_wait);
int
_raw_write_trylock_retry(rwlock_t *rw)
{
int count = spin_retry;
while (count-- > 0) {
atomic_inc(&spin_retry_counter);
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
return 1;
}
return 0;
}
EXPORT_SYMBOL(_raw_write_trylock_retry);

4
include/asm-s390/lowcore.h
View file

@ -90,7 +90,6 @@
#define __LC_SYSTEM_TIMER 0x278
#define __LC_LAST_UPDATE_CLOCK 0x280
#define __LC_STEAL_CLOCK 0x288
#define __LC_DIAG44_OPCODE 0x290
#define __LC_KERNEL_STACK 0xD40
#define __LC_THREAD_INFO 0xD48
#define __LC_ASYNC_STACK 0xD50
@ -286,8 +285,7 @@ struct _lowcore
__u64 system_timer; /* 0x278 */
__u64 last_update_clock; /* 0x280 */
__u64 steal_clock; /* 0x288 */
__u32 diag44_opcode; /* 0x290 */
__u8 pad8[0xc00-0x294]; /* 0x294 */
__u8 pad8[0xc00-0x290]; /* 0x290 */
/* System info area */
__u64 save_area[16]; /* 0xc00 */
__u8 pad9[0xd40-0xc80]; /* 0xc80 */

5
include/asm-s390/processor.h
View file

@ -203,7 +203,10 @@ unsigned long get_wchan(struct task_struct *p);
# define cpu_relax() asm volatile ("diag 0,0,68" : : : "memory")
#else /* __s390x__ */
# define cpu_relax() \
asm volatile ("ex 0,%0" : : "i" (__LC_DIAG44_OPCODE) : "memory")
do { \
if (MACHINE_HAS_DIAG44) \
asm volatile ("diag 0,0,68" : : : "memory"); \
} while (0)
#endif /* __s390x__ */
/*

246
include/asm-s390/spinlock.h
View file

@ -11,21 +11,16 @@
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#ifdef __s390x__
/*
* Grmph, take care of %&#! user space programs that include
* asm/spinlock.h. The diagnose is only available in kernel
* context.
*/
#ifdef __KERNEL__
#include <asm/lowcore.h>
#define __DIAG44_INSN "ex"
#define __DIAG44_OPERAND __LC_DIAG44_OPCODE
#else
#define __DIAG44_INSN "#"
#define __DIAG44_OPERAND 0
#endif
#endif /* __s390x__ */
static inline int
_raw_compare_and_swap(volatile unsigned int *lock,
unsigned int old, unsigned int new)
{
asm volatile ("cs %0,%3,0(%4)"
: "=d" (old), "=m" (*lock)
: "0" (old), "d" (new), "a" (lock), "m" (*lock)
: "cc", "memory" );
return old;
}
/*
* Simple spin lock operations. There are two variants, one clears IRQ's
@ -41,58 +36,35 @@ typedef struct {
#endif
} __attribute__ ((aligned (4))) spinlock_t;
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
#define spin_lock_init(lp) do { (lp)->lock = 0; } while(0)
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
#define spin_lock_init(lp) do { (lp)->lock = 0; } while(0)
#define spin_unlock_wait(lp) do { barrier(); } while(((volatile spinlock_t *)(lp))->lock)
#define spin_is_locked(x) ((x)->lock != 0)
#define spin_is_locked(x) ((x)->lock != 0)
#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
extern inline void _raw_spin_lock(spinlock_t *lp)
extern void _raw_spin_lock_wait(spinlock_t *lp, unsigned int pc);
extern int _raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc);
static inline void _raw_spin_lock(spinlock_t *lp)
{
#ifndef __s390x__
unsigned int reg1, reg2;
__asm__ __volatile__(" bras %0,1f\n"
"0: diag 0,0,68\n"
"1: slr %1,%1\n"
" cs %1,%0,0(%3)\n"
" jl 0b\n"
: "=&d" (reg1), "=&d" (reg2), "=m" (lp->lock)
: "a" (&lp->lock), "m" (lp->lock)
: "cc", "memory" );
#else /* __s390x__ */
unsigned long reg1, reg2;
__asm__ __volatile__(" bras %1,1f\n"
"0: " __DIAG44_INSN " 0,%4\n"
"1: slr %0,%0\n"
" cs %0,%1,0(%3)\n"
" jl 0b\n"
: "=&d" (reg1), "=&d" (reg2), "=m" (lp->lock)
: "a" (&lp->lock), "i" (__DIAG44_OPERAND),
"m" (lp->lock) : "cc", "memory" );
#endif /* __s390x__ */
unsigned long pc = (unsigned long) __builtin_return_address(0);
if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
_raw_spin_lock_wait(lp, pc);
}
extern inline int _raw_spin_trylock(spinlock_t *lp)
static inline int _raw_spin_trylock(spinlock_t *lp)
{
unsigned long reg;
unsigned int result;
unsigned long pc = (unsigned long) __builtin_return_address(0);
__asm__ __volatile__(" basr %1,0\n"
"0: cs %0,%1,0(%3)"
: "=d" (result), "=&d" (reg), "=m" (lp->lock)
: "a" (&lp->lock), "m" (lp->lock), "0" (0)
: "cc", "memory" );
return !result;
if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
return 1;
return _raw_spin_trylock_retry(lp, pc);
}
extern inline void _raw_spin_unlock(spinlock_t *lp)
static inline void _raw_spin_unlock(spinlock_t *lp)
{
unsigned int old;
__asm__ __volatile__("cs %0,%3,0(%4)"
: "=d" (old), "=m" (lp->lock)
: "0" (lp->lock), "d" (0), "a" (lp)
: "cc", "memory" );
_raw_compare_and_swap(&lp->lock, lp->lock, 0);
}
/*
@ -106,7 +78,7 @@ extern inline void _raw_spin_unlock(spinlock_t *lp)
* read-locks.
*/
typedef struct {
volatile unsigned long lock;
volatile unsigned int lock;
volatile unsigned long owner_pc;
#ifdef CONFIG_PREEMPT
unsigned int break_lock;
@ -129,123 +101,55 @@ typedef struct {
*/
#define write_can_lock(x) ((x)->lock == 0)
#ifndef __s390x__
#define _raw_read_lock(rw) \
asm volatile(" l 2,0(%1)\n" \
" j 1f\n" \
"0: diag 0,0,68\n" \
"1: la 2,0(2)\n" /* clear high (=write) bit */ \
" la 3,1(2)\n" /* one more reader */ \
" cs 2,3,0(%1)\n" /* try to write new value */ \
" jl 0b" \
: "=m" ((rw)->lock) : "a" (&(rw)->lock), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#else /* __s390x__ */
#define _raw_read_lock(rw) \
asm volatile(" lg 2,0(%1)\n" \
" j 1f\n" \
"0: " __DIAG44_INSN " 0,%2\n" \
"1: nihh 2,0x7fff\n" /* clear high (=write) bit */ \
" la 3,1(2)\n" /* one more reader */ \
" csg 2,3,0(%1)\n" /* try to write new value */ \
" jl 0b" \
: "=m" ((rw)->lock) \
: "a" (&(rw)->lock), "i" (__DIAG44_OPERAND), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#endif /* __s390x__ */
extern void _raw_read_lock_wait(rwlock_t *lp);
extern int _raw_read_trylock_retry(rwlock_t *lp);
extern void _raw_write_lock_wait(rwlock_t *lp);
extern int _raw_write_trylock_retry(rwlock_t *lp);
#ifndef __s390x__
#define _raw_read_unlock(rw) \
asm volatile(" l 2,0(%1)\n" \
" j 1f\n" \
"0: diag 0,0,68\n" \
"1: lr 3,2\n" \
" ahi 3,-1\n" /* one less reader */ \
" cs 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) : "a" (&(rw)->lock), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#else /* __s390x__ */
#define _raw_read_unlock(rw) \
asm volatile(" lg 2,0(%1)\n" \
" j 1f\n" \
"0: " __DIAG44_INSN " 0,%2\n" \
"1: lgr 3,2\n" \
" bctgr 3,0\n" /* one less reader */ \
" csg 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) \
: "a" (&(rw)->lock), "i" (__DIAG44_OPERAND), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#endif /* __s390x__ */
#ifndef __s390x__
#define _raw_write_lock(rw) \
asm volatile(" lhi 3,1\n" \
" sll 3,31\n" /* new lock value = 0x80000000 */ \
" j 1f\n" \
"0: diag 0,0,68\n" \
"1: slr 2,2\n" /* old lock value must be 0 */ \
" cs 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) : "a" (&(rw)->lock), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#else /* __s390x__ */
#define _raw_write_lock(rw) \
asm volatile(" llihh 3,0x8000\n" /* new lock value = 0x80...0 */ \
" j 1f\n" \
"0: " __DIAG44_INSN " 0,%2\n" \
"1: slgr 2,2\n" /* old lock value must be 0 */ \
" csg 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) \
: "a" (&(rw)->lock), "i" (__DIAG44_OPERAND), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#endif /* __s390x__ */
#ifndef __s390x__
#define _raw_write_unlock(rw) \
asm volatile(" slr 3,3\n" /* new lock value = 0 */ \
" j 1f\n" \
"0: diag 0,0,68\n" \
"1: lhi 2,1\n" \
" sll 2,31\n" /* old lock value must be 0x80000000 */ \
" cs 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) : "a" (&(rw)->lock), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#else /* __s390x__ */
#define _raw_write_unlock(rw) \
asm volatile(" slgr 3,3\n" /* new lock value = 0 */ \
" j 1f\n" \
"0: " __DIAG44_INSN " 0,%2\n" \
"1: llihh 2,0x8000\n" /* old lock value must be 0x8..0 */\
" csg 2,3,0(%1)\n" \
" jl 0b" \
: "=m" ((rw)->lock) \
: "a" (&(rw)->lock), "i" (__DIAG44_OPERAND), \
"m" ((rw)->lock) : "2", "3", "cc", "memory" )
#endif /* __s390x__ */
#define _raw_read_trylock(lock) generic_raw_read_trylock(lock)
extern inline int _raw_write_trylock(rwlock_t *rw)
static inline void _raw_read_lock(rwlock_t *rw)
{
unsigned long result, reg;
unsigned int old;
old = rw->lock & 0x7fffffffU;
if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
_raw_read_lock_wait(rw);
}
__asm__ __volatile__(
#ifndef __s390x__
" lhi %1,1\n"
" sll %1,31\n"
" cs %0,%1,0(%3)"
#else /* __s390x__ */
" llihh %1,0x8000\n"
"0: csg %0,%1,0(%3)\n"
#endif /* __s390x__ */
: "=d" (result), "=&d" (reg), "=m" (rw->lock)
: "a" (&rw->lock), "m" (rw->lock), "0" (0UL)
: "cc", "memory" );
return result == 0;
static inline void _raw_read_unlock(rwlock_t *rw)
{
unsigned int old, cmp;
old = rw->lock;
do {
cmp = old;
old = _raw_compare_and_swap(&rw->lock, old, old - 1);
} while (cmp != old);
}
static inline void _raw_write_lock(rwlock_t *rw)
{
if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
_raw_write_lock_wait(rw);
}
static inline void _raw_write_unlock(rwlock_t *rw)
{
_raw_compare_and_swap(&rw->lock, 0x80000000, 0);
}
static inline int _raw_read_trylock(rwlock_t *rw)
{
unsigned int old;
old = rw->lock & 0x7fffffffU;
if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
return 1;
return _raw_read_trylock_retry(rw);
}
static inline int _raw_write_trylock(rwlock_t *rw)
{
if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
return 1;
return _raw_write_trylock_retry(rw);
}
#endif /* __ASM_SPINLOCK_H */

1
include/linux/sysctl.h
View file

@ -145,6 +145,7 @@ enum
KERN_BOOTLOADER_TYPE=67, /* int: boot loader type */
KERN_RANDOMIZE=68, /* int: randomize virtual address space */
KERN_SETUID_DUMPABLE=69, /* int: behaviour of dumps for setuid core */
KERN_SPIN_RETRY=70, /* int: number of spinlock retries */
};

12
kernel/sysctl.c
View file

@ -114,6 +114,7 @@ extern int unaligned_enabled;
extern int sysctl_ieee_emulation_warnings;
#endif
extern int sysctl_userprocess_debug;
extern int spin_retry;
#endif
extern int sysctl_hz_timer;
@ -647,7 +648,16 @@ static ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#if defined(CONFIG_ARCH_S390)
{
.ctl_name = KERN_SPIN_RETRY,
.procname = "spin_retry",
.data = &spin_retry,
.maxlen = sizeof (int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#endif
{ .ctl_name = 0 }
};