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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/parisc
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/parisc')
-rw-r--r--arch/parisc/kernel/Makefile2
-rw-r--r--arch/parisc/kernel/parisc_ksyms.c5
-rw-r--r--arch/parisc/kernel/semaphore.c102
3 files changed, 1 insertions, 108 deletions
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 27827bc3717e..1f6585a56f97 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,7 @@ AFLAGS_pacache.o := -traditional
9 9
10obj-y := cache.o pacache.o setup.o traps.o time.o irq.o \ 10obj-y := cache.o pacache.o setup.o traps.o time.o irq.o \
11 pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \ 11 pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
12 ptrace.o hardware.o inventory.o drivers.o semaphore.o \ 12 ptrace.o hardware.o inventory.o drivers.o \
13 signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \ 13 signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
14 process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \ 14 process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
15 topology.o 15 topology.o
diff --git a/arch/parisc/kernel/parisc_ksyms.c b/arch/parisc/kernel/parisc_ksyms.c
index 7aca704e96f0..5b7fc4aa044d 100644
--- a/arch/parisc/kernel/parisc_ksyms.c
+++ b/arch/parisc/kernel/parisc_ksyms.c
@@ -69,11 +69,6 @@ EXPORT_SYMBOL(memcpy_toio);
69EXPORT_SYMBOL(memcpy_fromio); 69EXPORT_SYMBOL(memcpy_fromio);
70EXPORT_SYMBOL(memset_io); 70EXPORT_SYMBOL(memset_io);
71 71
72#include <asm/semaphore.h>
73EXPORT_SYMBOL(__up);
74EXPORT_SYMBOL(__down_interruptible);
75EXPORT_SYMBOL(__down);
76
77extern void $$divI(void); 72extern void $$divI(void);
78extern void $$divU(void); 73extern void $$divU(void);
79extern void $$remI(void); 74extern void $$remI(void);
diff --git a/arch/parisc/kernel/semaphore.c b/arch/parisc/kernel/semaphore.c
deleted file mode 100644
index ee806bcc3726..000000000000
--- a/arch/parisc/kernel/semaphore.c
+++ /dev/null
@@ -1,102 +0,0 @@
1/*
2 * Semaphore implementation Copyright (c) 2001 Matthew Wilcox, Hewlett-Packard
3 */
4
5#include <linux/sched.h>
6#include <linux/spinlock.h>
7#include <linux/errno.h>
8#include <linux/init.h>
9
10/*
11 * Semaphores are complex as we wish to avoid using two variables.
12 * `count' has multiple roles, depending on its value. If it is positive
13 * or zero, there are no waiters. The functions here will never be
14 * called; see <asm/semaphore.h>
15 *
16 * When count is -1 it indicates there is at least one task waiting
17 * for the semaphore.
18 *
19 * When count is less than that, there are '- count - 1' wakeups
20 * pending. ie if it has value -3, there are 2 wakeups pending.
21 *
22 * Note that these functions are only called when there is contention
23 * on the lock, and as such all this is the "non-critical" part of the
24 * whole semaphore business. The critical part is the inline stuff in
25 * <asm/semaphore.h> where we want to avoid any extra jumps and calls.
26 */
27void __up(struct semaphore *sem)
28{
29 sem->count--;
30 wake_up(&sem->wait);
31}
32
33#define wakers(count) (-1 - count)
34
35#define DOWN_HEAD \
36 int ret = 0; \
37 DECLARE_WAITQUEUE(wait, current); \
38 \
39 /* Note that someone is waiting */ \
40 if (sem->count == 0) \
41 sem->count = -1; \
42 \
43 /* protected by the sentry still -- use unlocked version */ \
44 wait.flags = WQ_FLAG_EXCLUSIVE; \
45 __add_wait_queue_tail(&sem->wait, &wait); \
46 lost_race: \
47 spin_unlock_irq(&sem->sentry); \
48
49#define DOWN_TAIL \
50 spin_lock_irq(&sem->sentry); \
51 if (wakers(sem->count) == 0 && ret == 0) \
52 goto lost_race; /* Someone stole our wakeup */ \
53 __remove_wait_queue(&sem->wait, &wait); \
54 current->state = TASK_RUNNING; \
55 if (!waitqueue_active(&sem->wait) && (sem->count < 0)) \
56 sem->count = wakers(sem->count);
57
58#define UPDATE_COUNT \
59 sem->count += (sem->count < 0) ? 1 : - 1;
60
61
62void __sched __down(struct semaphore * sem)
63{
64 DOWN_HEAD
65
66 for(;;) {
67 set_task_state(current, TASK_UNINTERRUPTIBLE);
68 /* we can _read_ this without the sentry */
69 if (sem->count != -1)
70 break;
71 schedule();
72 }
73
74 DOWN_TAIL
75 UPDATE_COUNT
76}
77
78int __sched __down_interruptible(struct semaphore * sem)
79{
80 DOWN_HEAD
81
82 for(;;) {
83 set_task_state(current, TASK_INTERRUPTIBLE);
84 /* we can _read_ this without the sentry */
85 if (sem->count != -1)
86 break;
87
88 if (signal_pending(current)) {
89 ret = -EINTR;
90 break;
91 }
92 schedule();
93 }
94
95 DOWN_TAIL
96
97 if (!ret) {
98 UPDATE_COUNT
99 }
100
101 return ret;
102}