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authorMatthew Wilcox <matthew@wil.cx>2008-03-07 21:55:58 -0500
committerMatthew Wilcox <willy@linux.intel.com>2008-04-17 10:42:34 -0400
commit64ac24e738823161693bf791f87adc802cf529ff (patch)
tree19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/sparc64
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/sparc64')
-rw-r--r--arch/sparc64/kernel/Makefile2
-rw-r--r--arch/sparc64/kernel/semaphore.c254
-rw-r--r--arch/sparc64/kernel/sparc64_ksyms.c6
3 files changed, 1 insertions, 261 deletions
diff --git a/arch/sparc64/kernel/Makefile b/arch/sparc64/kernel/Makefile
index 1bf5b187de49..459462e80a12 100644
--- a/arch/sparc64/kernel/Makefile
+++ b/arch/sparc64/kernel/Makefile
@@ -10,7 +10,7 @@ extra-y := head.o init_task.o vmlinux.lds
10obj-y := process.o setup.o cpu.o idprom.o \ 10obj-y := process.o setup.o cpu.o idprom.o \
11 traps.o auxio.o una_asm.o sysfs.o iommu.o \ 11 traps.o auxio.o una_asm.o sysfs.o iommu.o \
12 irq.o ptrace.o time.o sys_sparc.o signal.o \ 12 irq.o ptrace.o time.o sys_sparc.o signal.o \
13 unaligned.o central.o pci.o starfire.o semaphore.o \ 13 unaligned.o central.o pci.o starfire.o \
14 power.o sbus.o sparc64_ksyms.o chmc.o \ 14 power.o sbus.o sparc64_ksyms.o chmc.o \
15 visemul.o prom.o of_device.o hvapi.o sstate.o mdesc.o 15 visemul.o prom.o of_device.o hvapi.o sstate.o mdesc.o
16 16
diff --git a/arch/sparc64/kernel/semaphore.c b/arch/sparc64/kernel/semaphore.c
deleted file mode 100644
index 9974a6899551..000000000000
--- a/arch/sparc64/kernel/semaphore.c
+++ /dev/null
@@ -1,254 +0,0 @@
1/* semaphore.c: Sparc64 semaphore implementation.
2 *
3 * This is basically the PPC semaphore scheme ported to use
4 * the sparc64 atomic instructions, so see the PPC code for
5 * credits.
6 */
7
8#include <linux/sched.h>
9#include <linux/errno.h>
10#include <linux/init.h>
11
12/*
13 * Atomically update sem->count.
14 * This does the equivalent of the following:
15 *
16 * old_count = sem->count;
17 * tmp = MAX(old_count, 0) + incr;
18 * sem->count = tmp;
19 * return old_count;
20 */
21static inline int __sem_update_count(struct semaphore *sem, int incr)
22{
23 int old_count, tmp;
24
25 __asm__ __volatile__("\n"
26" ! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n"
27"1: ldsw [%3], %0\n"
28" mov %0, %1\n"
29" cmp %0, 0\n"
30" movl %%icc, 0, %1\n"
31" add %1, %4, %1\n"
32" cas [%3], %0, %1\n"
33" cmp %0, %1\n"
34" membar #StoreLoad | #StoreStore\n"
35" bne,pn %%icc, 1b\n"
36" nop\n"
37 : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
38 : "r" (&sem->count), "r" (incr), "m" (sem->count)
39 : "cc");
40
41 return old_count;
42}
43
44static void __up(struct semaphore *sem)
45{
46 __sem_update_count(sem, 1);
47 wake_up(&sem->wait);
48}
49
50void up(struct semaphore *sem)
51{
52 /* This atomically does:
53 * old_val = sem->count;
54 * new_val = sem->count + 1;
55 * sem->count = new_val;
56 * if (old_val < 0)
57 * __up(sem);
58 *
59 * The (old_val < 0) test is equivalent to
60 * the more straightforward (new_val <= 0),
61 * but it is easier to test the former because
62 * of how the CAS instruction works.
63 */
64
65 __asm__ __volatile__("\n"
66" ! up sem(%0)\n"
67" membar #StoreLoad | #LoadLoad\n"
68"1: lduw [%0], %%g1\n"
69" add %%g1, 1, %%g7\n"
70" cas [%0], %%g1, %%g7\n"
71" cmp %%g1, %%g7\n"
72" bne,pn %%icc, 1b\n"
73" addcc %%g7, 1, %%g0\n"
74" membar #StoreLoad | #StoreStore\n"
75" ble,pn %%icc, 3f\n"
76" nop\n"
77"2:\n"
78" .subsection 2\n"
79"3: mov %0, %%g1\n"
80" save %%sp, -160, %%sp\n"
81" call %1\n"
82" mov %%g1, %%o0\n"
83" ba,pt %%xcc, 2b\n"
84" restore\n"
85" .previous\n"
86 : : "r" (sem), "i" (__up)
87 : "g1", "g2", "g3", "g7", "memory", "cc");
88}
89
90static void __sched __down(struct semaphore * sem)
91{
92 struct task_struct *tsk = current;
93 DECLARE_WAITQUEUE(wait, tsk);
94
95 tsk->state = TASK_UNINTERRUPTIBLE;
96 add_wait_queue_exclusive(&sem->wait, &wait);
97
98 while (__sem_update_count(sem, -1) <= 0) {
99 schedule();
100 tsk->state = TASK_UNINTERRUPTIBLE;
101 }
102 remove_wait_queue(&sem->wait, &wait);
103 tsk->state = TASK_RUNNING;
104
105 wake_up(&sem->wait);
106}
107
108void __sched down(struct semaphore *sem)
109{
110 might_sleep();
111 /* This atomically does:
112 * old_val = sem->count;
113 * new_val = sem->count - 1;
114 * sem->count = new_val;
115 * if (old_val < 1)
116 * __down(sem);
117 *
118 * The (old_val < 1) test is equivalent to
119 * the more straightforward (new_val < 0),
120 * but it is easier to test the former because
121 * of how the CAS instruction works.
122 */
123
124 __asm__ __volatile__("\n"
125" ! down sem(%0)\n"
126"1: lduw [%0], %%g1\n"
127" sub %%g1, 1, %%g7\n"
128" cas [%0], %%g1, %%g7\n"
129" cmp %%g1, %%g7\n"
130" bne,pn %%icc, 1b\n"
131" cmp %%g7, 1\n"
132" membar #StoreLoad | #StoreStore\n"
133" bl,pn %%icc, 3f\n"
134" nop\n"
135"2:\n"
136" .subsection 2\n"
137"3: mov %0, %%g1\n"
138" save %%sp, -160, %%sp\n"
139" call %1\n"
140" mov %%g1, %%o0\n"
141" ba,pt %%xcc, 2b\n"
142" restore\n"
143" .previous\n"
144 : : "r" (sem), "i" (__down)
145 : "g1", "g2", "g3", "g7", "memory", "cc");
146}
147
148int down_trylock(struct semaphore *sem)
149{
150 int ret;
151
152 /* This atomically does:
153 * old_val = sem->count;
154 * new_val = sem->count - 1;
155 * if (old_val < 1) {
156 * ret = 1;
157 * } else {
158 * sem->count = new_val;
159 * ret = 0;
160 * }
161 *
162 * The (old_val < 1) test is equivalent to
163 * the more straightforward (new_val < 0),
164 * but it is easier to test the former because
165 * of how the CAS instruction works.
166 */
167
168 __asm__ __volatile__("\n"
169" ! down_trylock sem(%1) ret(%0)\n"
170"1: lduw [%1], %%g1\n"
171" sub %%g1, 1, %%g7\n"
172" cmp %%g1, 1\n"
173" bl,pn %%icc, 2f\n"
174" mov 1, %0\n"
175" cas [%1], %%g1, %%g7\n"
176" cmp %%g1, %%g7\n"
177" bne,pn %%icc, 1b\n"
178" mov 0, %0\n"
179" membar #StoreLoad | #StoreStore\n"
180"2:\n"
181 : "=&r" (ret)
182 : "r" (sem)
183 : "g1", "g7", "memory", "cc");
184
185 return ret;
186}
187
188static int __sched __down_interruptible(struct semaphore * sem)
189{
190 int retval = 0;
191 struct task_struct *tsk = current;
192 DECLARE_WAITQUEUE(wait, tsk);
193
194 tsk->state = TASK_INTERRUPTIBLE;
195 add_wait_queue_exclusive(&sem->wait, &wait);
196
197 while (__sem_update_count(sem, -1) <= 0) {
198 if (signal_pending(current)) {
199 __sem_update_count(sem, 0);
200 retval = -EINTR;
201 break;
202 }
203 schedule();
204 tsk->state = TASK_INTERRUPTIBLE;
205 }
206 tsk->state = TASK_RUNNING;
207 remove_wait_queue(&sem->wait, &wait);
208 wake_up(&sem->wait);
209 return retval;
210}
211
212int __sched down_interruptible(struct semaphore *sem)
213{
214 int ret = 0;
215
216 might_sleep();
217 /* This atomically does:
218 * old_val = sem->count;
219 * new_val = sem->count - 1;
220 * sem->count = new_val;
221 * if (old_val < 1)
222 * ret = __down_interruptible(sem);
223 *
224 * The (old_val < 1) test is equivalent to
225 * the more straightforward (new_val < 0),
226 * but it is easier to test the former because
227 * of how the CAS instruction works.
228 */
229
230 __asm__ __volatile__("\n"
231" ! down_interruptible sem(%2) ret(%0)\n"
232"1: lduw [%2], %%g1\n"
233" sub %%g1, 1, %%g7\n"
234" cas [%2], %%g1, %%g7\n"
235" cmp %%g1, %%g7\n"
236" bne,pn %%icc, 1b\n"
237" cmp %%g7, 1\n"
238" membar #StoreLoad | #StoreStore\n"
239" bl,pn %%icc, 3f\n"
240" nop\n"
241"2:\n"
242" .subsection 2\n"
243"3: mov %2, %%g1\n"
244" save %%sp, -160, %%sp\n"
245" call %3\n"
246" mov %%g1, %%o0\n"
247" ba,pt %%xcc, 2b\n"
248" restore\n"
249" .previous\n"
250 : "=r" (ret)
251 : "0" (ret), "r" (sem), "i" (__down_interruptible)
252 : "g1", "g2", "g3", "g7", "memory", "cc");
253 return ret;
254}
diff --git a/arch/sparc64/kernel/sparc64_ksyms.c b/arch/sparc64/kernel/sparc64_ksyms.c
index 51fa773f38c9..051b8d9cb989 100644
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/arch/sparc64/kernel/sparc64_ksyms.c
@@ -130,12 +130,6 @@ EXPORT_SYMBOL(_mcount);
130 130
131EXPORT_SYMBOL(sparc64_get_clock_tick); 131EXPORT_SYMBOL(sparc64_get_clock_tick);
132 132
133/* semaphores */
134EXPORT_SYMBOL(down);
135EXPORT_SYMBOL(down_trylock);
136EXPORT_SYMBOL(down_interruptible);
137EXPORT_SYMBOL(up);
138
139/* RW semaphores */ 133/* RW semaphores */
140EXPORT_SYMBOL(__down_read); 134EXPORT_SYMBOL(__down_read);
141EXPORT_SYMBOL(__down_read_trylock); 135EXPORT_SYMBOL(__down_read_trylock);
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