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Commit 951f22d5 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Linus Torvalds
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[PATCH] s390: spin lock retry 



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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8449d003

arch/s390/kernel/head64.S

+0 −3
Original line number Diff line number Diff line
@@ -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

arch/s390/kernel/setup.c

+0 −6
Original line number Diff line number Diff line
@@ -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);

}

arch/s390/lib/Makefile

+2 −2
Original line number Diff line number Diff line
@@ -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

arch/s390/lib/spinlock.c

0 → 100644
+133 −0
Original line number Diff line number Diff line 
/*

 *  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);

include/asm-s390/lowcore.h

+1 −3
Original line number Diff line number Diff line
@@ -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 */