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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/m68knommu
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/m68knommu')
-rw-r--r--arch/m68knommu/kernel/Makefile2
-rw-r--r--arch/m68knommu/kernel/m68k_ksyms.c6
-rw-r--r--arch/m68knommu/kernel/semaphore.c133
-rw-r--r--arch/m68knommu/lib/Makefile2
-rw-r--r--arch/m68knommu/lib/semaphore.S66
5 files changed, 2 insertions, 207 deletions
diff --git a/arch/m68knommu/kernel/Makefile b/arch/m68knommu/kernel/Makefile
index 1524b39ad63f..f0eab3dedb5a 100644
--- a/arch/m68knommu/kernel/Makefile
+++ b/arch/m68knommu/kernel/Makefile
@@ -5,7 +5,7 @@
5extra-y := vmlinux.lds 5extra-y := vmlinux.lds
6 6
7obj-y += dma.o entry.o init_task.o irq.o m68k_ksyms.o process.o ptrace.o \ 7obj-y += dma.o entry.o init_task.o irq.o m68k_ksyms.o process.o ptrace.o \
8 semaphore.o setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o 8 setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o
9 9
10obj-$(CONFIG_MODULES) += module.o 10obj-$(CONFIG_MODULES) += module.o
11obj-$(CONFIG_COMEMPCI) += comempci.o 11obj-$(CONFIG_COMEMPCI) += comempci.o
diff --git a/arch/m68knommu/kernel/m68k_ksyms.c b/arch/m68knommu/kernel/m68k_ksyms.c
index 53fad1490282..39fe0a7aec32 100644
--- a/arch/m68knommu/kernel/m68k_ksyms.c
+++ b/arch/m68knommu/kernel/m68k_ksyms.c
@@ -13,7 +13,6 @@
13#include <asm/pgalloc.h> 13#include <asm/pgalloc.h>
14#include <asm/irq.h> 14#include <asm/irq.h>
15#include <asm/io.h> 15#include <asm/io.h>
16#include <asm/semaphore.h>
17#include <asm/checksum.h> 16#include <asm/checksum.h>
18#include <asm/current.h> 17#include <asm/current.h>
19 18
@@ -39,11 +38,6 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
39EXPORT_SYMBOL(memcpy); 38EXPORT_SYMBOL(memcpy);
40EXPORT_SYMBOL(memset); 39EXPORT_SYMBOL(memset);
41 40
42EXPORT_SYMBOL(__down_failed);
43EXPORT_SYMBOL(__down_failed_interruptible);
44EXPORT_SYMBOL(__down_failed_trylock);
45EXPORT_SYMBOL(__up_wakeup);
46
47/* 41/*
48 * libgcc functions - functions that are used internally by the 42 * libgcc functions - functions that are used internally by the
49 * compiler... (prototypes are not correct though, but that 43 * compiler... (prototypes are not correct though, but that
diff --git a/arch/m68knommu/kernel/semaphore.c b/arch/m68knommu/kernel/semaphore.c
deleted file mode 100644
index bce2bc7d87c6..000000000000
--- a/arch/m68knommu/kernel/semaphore.c
+++ /dev/null
@@ -1,133 +0,0 @@
1/*
2 * Generic semaphore code. Buyer beware. Do your own
3 * specific changes in <asm/semaphore-helper.h>
4 */
5
6#include <linux/sched.h>
7#include <linux/err.h>
8#include <linux/init.h>
9#include <asm/semaphore-helper.h>
10
11#ifndef CONFIG_RMW_INSNS
12spinlock_t semaphore_wake_lock;
13#endif
14
15/*
16 * Semaphores are implemented using a two-way counter:
17 * The "count" variable is decremented for each process
18 * that tries to sleep, while the "waking" variable is
19 * incremented when the "up()" code goes to wake up waiting
20 * processes.
21 *
22 * Notably, the inline "up()" and "down()" functions can
23 * efficiently test if they need to do any extra work (up
24 * needs to do something only if count was negative before
25 * the increment operation.
26 *
27 * waking_non_zero() (from asm/semaphore.h) must execute
28 * atomically.
29 *
30 * When __up() is called, the count was negative before
31 * incrementing it, and we need to wake up somebody.
32 *
33 * This routine adds one to the count of processes that need to
34 * wake up and exit. ALL waiting processes actually wake up but
35 * only the one that gets to the "waking" field first will gate
36 * through and acquire the semaphore. The others will go back
37 * to sleep.
38 *
39 * Note that these functions are only called when there is
40 * contention on the lock, and as such all this is the
41 * "non-critical" part of the whole semaphore business. The
42 * critical part is the inline stuff in <asm/semaphore.h>
43 * where we want to avoid any extra jumps and calls.
44 */
45void __up(struct semaphore *sem)
46{
47 wake_one_more(sem);
48 wake_up(&sem->wait);
49}
50
51/*
52 * Perform the "down" function. Return zero for semaphore acquired,
53 * return negative for signalled out of the function.
54 *
55 * If called from __down, the return is ignored and the wait loop is
56 * not interruptible. This means that a task waiting on a semaphore
57 * using "down()" cannot be killed until someone does an "up()" on
58 * the semaphore.
59 *
60 * If called from __down_interruptible, the return value gets checked
61 * upon return. If the return value is negative then the task continues
62 * with the negative value in the return register (it can be tested by
63 * the caller).
64 *
65 * Either form may be used in conjunction with "up()".
66 *
67 */
68
69
70#define DOWN_HEAD(task_state) \
71 \
72 \
73 current->state = (task_state); \
74 add_wait_queue(&sem->wait, &wait); \
75 \
76 /* \
77 * Ok, we're set up. sem->count is known to be less than zero \
78 * so we must wait. \
79 * \
80 * We can let go the lock for purposes of waiting. \
81 * We re-acquire it after awaking so as to protect \
82 * all semaphore operations. \
83 * \
84 * If "up()" is called before we call waking_non_zero() then \
85 * we will catch it right away. If it is called later then \
86 * we will have to go through a wakeup cycle to catch it. \
87 * \
88 * Multiple waiters contend for the semaphore lock to see \
89 * who gets to gate through and who has to wait some more. \
90 */ \
91 for (;;) {
92
93#define DOWN_TAIL(task_state) \
94 current->state = (task_state); \
95 } \
96 current->state = TASK_RUNNING; \
97 remove_wait_queue(&sem->wait, &wait);
98
99void __sched __down(struct semaphore * sem)
100{
101 DECLARE_WAITQUEUE(wait, current);
102
103 DOWN_HEAD(TASK_UNINTERRUPTIBLE)
104 if (waking_non_zero(sem))
105 break;
106 schedule();
107 DOWN_TAIL(TASK_UNINTERRUPTIBLE)
108}
109
110int __sched __down_interruptible(struct semaphore * sem)
111{
112 DECLARE_WAITQUEUE(wait, current);
113 int ret = 0;
114
115 DOWN_HEAD(TASK_INTERRUPTIBLE)
116
117 ret = waking_non_zero_interruptible(sem, current);
118 if (ret)
119 {
120 if (ret == 1)
121 /* ret != 0 only if we get interrupted -arca */
122 ret = 0;
123 break;
124 }
125 schedule();
126 DOWN_TAIL(TASK_INTERRUPTIBLE)
127 return ret;
128}
129
130int __down_trylock(struct semaphore * sem)
131{
132 return waking_non_zero_trylock(sem);
133}
diff --git a/arch/m68knommu/lib/Makefile b/arch/m68knommu/lib/Makefile
index e051a7913987..d94d709665aa 100644
--- a/arch/m68knommu/lib/Makefile
+++ b/arch/m68knommu/lib/Makefile
@@ -4,4 +4,4 @@
4 4
5lib-y := ashldi3.o ashrdi3.o lshrdi3.o \ 5lib-y := ashldi3.o ashrdi3.o lshrdi3.o \
6 muldi3.o mulsi3.o divsi3.o udivsi3.o modsi3.o umodsi3.o \ 6 muldi3.o mulsi3.o divsi3.o udivsi3.o modsi3.o umodsi3.o \
7 checksum.o semaphore.o memcpy.o memset.o delay.o 7 checksum.o memcpy.o memset.o delay.o
diff --git a/arch/m68knommu/lib/semaphore.S b/arch/m68knommu/lib/semaphore.S
deleted file mode 100644
index 87c746034376..000000000000
--- a/arch/m68knommu/lib/semaphore.S
+++ /dev/null
@@ -1,66 +0,0 @@
1/*
2 * linux/arch/m68k/lib/semaphore.S
3 *
4 * Copyright (C) 1996 Linus Torvalds
5 *
6 * m68k version by Andreas Schwab
7 *
8 * MAR/1999 -- modified to support ColdFire (gerg@snapgear.com)
9 */
10
11#include <linux/linkage.h>
12#include <asm/semaphore.h>
13
14/*
15 * "down_failed" is called with the eventual return address
16 * in %a0, and the address of the semaphore in %a1. We need
17 * to increment the number of waiters on the semaphore,
18 * call "__down()", and then eventually return to try again.
19 */
20ENTRY(__down_failed)
21#ifdef CONFIG_COLDFIRE
22 subl #12,%sp
23 moveml %a0/%d0/%d1,(%sp)
24#else
25 moveml %a0/%d0/%d1,-(%sp)
26#endif
27 movel %a1,-(%sp)
28 jbsr __down
29 movel (%sp)+,%a1
30 movel (%sp)+,%d0
31 movel (%sp)+,%d1
32 rts
33
34ENTRY(__down_failed_interruptible)
35 movel %a0,-(%sp)
36 movel %d1,-(%sp)
37 movel %a1,-(%sp)
38 jbsr __down_interruptible
39 movel (%sp)+,%a1
40 movel (%sp)+,%d1
41 rts
42
43ENTRY(__up_wakeup)
44#ifdef CONFIG_COLDFIRE
45 subl #12,%sp
46 moveml %a0/%d0/%d1,(%sp)
47#else
48 moveml %a0/%d0/%d1,-(%sp)
49#endif
50 movel %a1,-(%sp)
51 jbsr __up
52 movel (%sp)+,%a1
53 movel (%sp)+,%d0
54 movel (%sp)+,%d1
55 rts
56
57ENTRY(__down_failed_trylock)
58 movel %a0,-(%sp)
59 movel %d1,-(%sp)
60 movel %a1,-(%sp)
61 jbsr __down_trylock
62 movel (%sp)+,%a1
63 movel (%sp)+,%d1
64 movel (%sp)+,%a0
65 rts
66
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