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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2005-07-27 14:44:57 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-07-27 19:26:04 -0400
commit951f22d5b1f0eaae35dafc669e3774a0c2084d10 (patch)
tree66c0131b576dadb98026da11d624df453c4c9a7c /arch
parent8449d003f323ca7a00eec38905d984ba5ec83a29 (diff)
[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: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/kernel/head64.S3
-rw-r--r--arch/s390/kernel/setup.c6
-rw-r--r--arch/s390/lib/Makefile4
-rw-r--r--arch/s390/lib/spinlock.c133
4 files changed, 135 insertions, 11 deletions
diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index f525c0c21250..28c50bdf7d40 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -658,10 +658,8 @@ startup:basr %r13,0 # get base
658# 658#
659 la %r1,0f-.LPG1(%r13) # set program check address 659 la %r1,0f-.LPG1(%r13) # set program check address
660 stg %r1,__LC_PGM_NEW_PSW+8 660 stg %r1,__LC_PGM_NEW_PSW+8
661 mvc __LC_DIAG44_OPCODE(8),.Lnop-.LPG1(%r13)
662 diag 0,0,0x44 # test diag 0x44 661 diag 0,0,0x44 # test diag 0x44
663 oi 7(%r12),32 # set diag44 flag 662 oi 7(%r12),32 # set diag44 flag
664 mvc __LC_DIAG44_OPCODE(8),.Ldiag44-.LPG1(%r13)
6650: 6630:
666 664
667# 665#
@@ -702,7 +700,6 @@ startup:basr %r13,0 # get base
702.L4malign:.quad 0xffffffffffc00000 700.L4malign:.quad 0xffffffffffc00000
703.Lscan2g:.quad 0x80000000 + 0x20000 - 8 # 2GB + 128K - 8 701.Lscan2g:.quad 0x80000000 + 0x20000 - 8 # 2GB + 128K - 8
704.Lnop: .long 0x07000700 702.Lnop: .long 0x07000700
705.Ldiag44:.long 0x83000044
706 703
707 .org PARMAREA-64 704 .org PARMAREA-64
708.Lduct: .long 0,0,0,0,0,0,0,0 705.Lduct: .long 0,0,0,0,0,0,0,0
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index a12183989a79..5ba5a5485da9 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -431,12 +431,6 @@ setup_lowcore(void)
431 ctl_set_bit(14, 29); 431 ctl_set_bit(14, 29);
432 } 432 }
433#endif 433#endif
434#ifdef CONFIG_ARCH_S390X
435 if (MACHINE_HAS_DIAG44)
436 lc->diag44_opcode = 0x83000044;
437 else
438 lc->diag44_opcode = 0x07000700;
439#endif /* CONFIG_ARCH_S390X */
440 set_prefix((u32)(unsigned long) lc); 434 set_prefix((u32)(unsigned long) lc);
441} 435}
442 436
diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile
index a8758b1d20a9..b701efa1f00e 100644
--- a/arch/s390/lib/Makefile
+++ b/arch/s390/lib/Makefile
@@ -5,5 +5,5 @@
5EXTRA_AFLAGS := -traditional 5EXTRA_AFLAGS := -traditional
6 6
7lib-y += delay.o string.o 7lib-y += delay.o string.o
8lib-$(CONFIG_ARCH_S390_31) += uaccess.o 8lib-$(CONFIG_ARCH_S390_31) += uaccess.o spinlock.o
9lib-$(CONFIG_ARCH_S390X) += uaccess64.o 9lib-$(CONFIG_ARCH_S390X) += uaccess64.o spinlock.o
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
new file mode 100644
index 000000000000..888b5596c195
--- /dev/null
+++ b/arch/s390/lib/spinlock.c
@@ -0,0 +1,133 @@
1/*
2 * arch/s390/lib/spinlock.c
3 * Out of line spinlock code.
4 *
5 * S390 version
6 * Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
8 */
9
10#include <linux/types.h>
11#include <linux/module.h>
12#include <linux/spinlock.h>
13#include <linux/init.h>
14#include <asm/io.h>
15
16atomic_t spin_retry_counter;
17int spin_retry = 1000;
18
19/**
20 * spin_retry= parameter
21 */
22static int __init spin_retry_setup(char *str)
23{
24 spin_retry = simple_strtoul(str, &str, 0);
25 return 1;
26}
27__setup("spin_retry=", spin_retry_setup);
28
29static inline void
30_diag44(void)
31{
32#ifdef __s390x__
33 if (MACHINE_HAS_DIAG44)
34#endif
35 asm volatile("diag 0,0,0x44");
36}
37
38void
39_raw_spin_lock_wait(spinlock_t *lp, unsigned int pc)
40{
41 int count = spin_retry;
42
43 while (1) {
44 if (count-- <= 0) {
45 _diag44();
46 count = spin_retry;
47 }
48 atomic_inc(&spin_retry_counter);
49 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
50 return;
51 }
52}
53EXPORT_SYMBOL(_raw_spin_lock_wait);
54
55int
56_raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc)
57{
58 int count = spin_retry;
59
60 while (count-- > 0) {
61 atomic_inc(&spin_retry_counter);
62 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
63 return 1;
64 }
65 return 0;
66}
67EXPORT_SYMBOL(_raw_spin_trylock_retry);
68
69void
70_raw_read_lock_wait(rwlock_t *rw)
71{
72 unsigned int old;
73 int count = spin_retry;
74
75 while (1) {
76 if (count-- <= 0) {
77 _diag44();
78 count = spin_retry;
79 }
80 atomic_inc(&spin_retry_counter);
81 old = rw->lock & 0x7fffffffU;
82 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
83 return;
84 }
85}
86EXPORT_SYMBOL(_raw_read_lock_wait);
87
88int
89_raw_read_trylock_retry(rwlock_t *rw)
90{
91 unsigned int old;
92 int count = spin_retry;
93
94 while (count-- > 0) {
95 atomic_inc(&spin_retry_counter);
96 old = rw->lock & 0x7fffffffU;
97 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
98 return 1;
99 }
100 return 0;
101}
102EXPORT_SYMBOL(_raw_read_trylock_retry);
103
104void
105_raw_write_lock_wait(rwlock_t *rw)
106{
107 int count = spin_retry;
108
109 while (1) {
110 if (count-- <= 0) {
111 _diag44();
112 count = spin_retry;
113 }
114 atomic_inc(&spin_retry_counter);
115 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
116 return;
117 }
118}
119EXPORT_SYMBOL(_raw_write_lock_wait);
120
121int
122_raw_write_trylock_retry(rwlock_t *rw)
123{
124 int count = spin_retry;
125
126 while (count-- > 0) {
127 atomic_inc(&spin_retry_counter);
128 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
129 return 1;
130 }
131 return 0;
132}
133EXPORT_SYMBOL(_raw_write_trylock_retry);