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>
author: Matthew Wilcox <matthew@wil.cx> 2008-03-07 21:55:58 -0500
committer: Matthew Wilcox <willy@linux.intel.com> 2008-04-17 10:42:34 -0400
commit: 64ac24e738823161693bf791f87adc802cf529ff (patch)
tree: 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/sh
parent: e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
5 files changed, 2 insertions, 152 deletions
diff --git a/arch/sh/kernel/Makefile_32 b/arch/sh/kernel/Makefile_32
index 62bf373266f7..4bbdce36b92b 100644
--- a/arch/sh/kernel/Makefile_32
+++ b/arch/sh/kernel/Makefile_32
@@ -5,7 +5,7 @@
 extra-y := head_32.o init_task.o vmlinux.lds
 obj-y   := debugtraps.o io.o io_generic.o irq.o machvec.o process_32.o \
-           ptrace_32.o semaphore.o setup.o signal_32.o sys_sh.o sys_sh32.o \
+           ptrace_32.o setup.o signal_32.o sys_sh.o sys_sh32.o \
           syscalls_32.o time_32.o topology.o traps.o traps_32.o
 obj-y                           += cpu/ timers/
diff --git a/arch/sh/kernel/Makefile_64 b/arch/sh/kernel/Makefile_64
index e01283d49cbf..6edf53b93d94 100644
--- a/arch/sh/kernel/Makefile_64
+++ b/arch/sh/kernel/Makefile_64
@@ -1,7 +1,7 @@
 extra-y := head_64.o init_task.o vmlinux.lds
 obj-y   := debugtraps.o io.o io_generic.o irq.o machvec.o process_64.o \
-           ptrace_64.o semaphore.o setup.o signal_64.o sys_sh.o sys_sh64.o \
+           ptrace_64.o setup.o signal_64.o sys_sh.o sys_sh64.o \
           syscalls_64.o time_64.o topology.o traps.o traps_64.o
 obj-y                           += cpu/ timers/
diff --git a/arch/sh/kernel/semaphore.c b/arch/sh/kernel/semaphore.c
deleted file mode 100644
index 184119eeae56..000000000000
--- a/arch/sh/kernel/semaphore.c
+++ /dev/null
@@ -1,139 +0,0 @@
-/*
- * Just taken from alpha implementation.
- * This can't work well, perhaps.
- */
-/*
- *  Generic semaphore code. Buyer beware. Do your own
- * specific changes in <asm/semaphore-helper.h>
- */
-#include <linux/errno.h>
-#include <linux/sched.h>
-#include <linux/wait.h>
-#include <linux/init.h>
-#include <asm/semaphore.h>
-#include <asm/semaphore-helper.h>
-DEFINE_SPINLOCK(semaphore_wake_lock);
-/*
- * Semaphores are implemented using a two-way counter:
- * The "count" variable is decremented for each process
- * that tries to sleep, while the "waking" variable is
- * incremented when the "up()" code goes to wake up waiting
- * processes.
- *
- * Notably, the inline "up()" and "down()" functions can
- * efficiently test if they need to do any extra work (up
- * needs to do something only if count was negative before
- * the increment operation.
- *
- * waking_non_zero() (from asm/semaphore.h) must execute
- * atomically.
- *
- * When __up() is called, the count was negative before
- * incrementing it, and we need to wake up somebody.
- *
- * This routine adds one to the count of processes that need to
- * wake up and exit.  ALL waiting processes actually wake up but
- * only the one that gets to the "waking" field first will gate
- * through and acquire the semaphore.  The others will go back
- * to sleep.
- *
- * Note that these functions are only called when there is
- * contention on the lock, and as such all this is the
- * "non-critical" part of the whole semaphore business. The
- * critical part is the inline stuff in <asm/semaphore.h>
- * where we want to avoid any extra jumps and calls.
- */
-void __up(struct semaphore *sem)
-{
-        wake_one_more(sem);
-        wake_up(&sem->wait);
-}
-/*
- * Perform the "down" function.  Return zero for semaphore acquired,
- * return negative for signalled out of the function.
- *
- * If called from __down, the return is ignored and the wait loop is
- * not interruptible.  This means that a task waiting on a semaphore
- * using "down()" cannot be killed until someone does an "up()" on
- * the semaphore.
- *
- * If called from __down_interruptible, the return value gets checked
- * upon return.  If the return value is negative then the task continues
- * with the negative value in the return register (it can be tested by
- * the caller).
- *
- * Either form may be used in conjunction with "up()".
- *
- */
-#define DOWN_VAR                                \
-        struct task_struct *tsk = current;      \
-        wait_queue_t wait;                      \
-        init_waitqueue_entry(&wait, tsk);
-#define DOWN_HEAD(task_state)                                           \
-                                                                        \
-                                                                        \
-        tsk->state = (task_state);                                      \
-        add_wait_queue(&sem->wait, &wait);                              \
-                                                                        \
-        /*                                                              \
-         * Ok, we're set up.  sem->count is known to be less than zero  \
-         * so we must wait.                                             \
-         *                                                              \
-         * We can let go the lock for purposes of waiting.              \
-         * We re-acquire it after awaking so as to protect              \
-         * all semaphore operations.                                    \
-         *                                                              \
-         * If "up()" is called before we call waking_non_zero() then    \
-         * we will catch it right away.  If it is called later then     \
-         * we will have to go through a wakeup cycle to catch it.       \
-         *                                                              \
-         * Multiple waiters contend for the semaphore lock to see       \
-         * who gets to gate through and who has to wait some more.      \
-         */                                                             \
-        for (;;) {
-#define DOWN_TAIL(task_state)                   \
-                tsk->state = (task_state);      \
-        }                                       \
-        tsk->state = TASK_RUNNING;              \
-        remove_wait_queue(&sem->wait, &wait);
-void __sched __down(struct semaphore * sem)
-{
-        DOWN_VAR
-        DOWN_HEAD(TASK_UNINTERRUPTIBLE)
-        if (waking_non_zero(sem))
-                break;
-        schedule();
-        DOWN_TAIL(TASK_UNINTERRUPTIBLE)
-}
-int __sched __down_interruptible(struct semaphore * sem)
-{
-        int ret = 0;
-        DOWN_VAR
-        DOWN_HEAD(TASK_INTERRUPTIBLE)
-        ret = waking_non_zero_interruptible(sem, tsk);
-        if (ret)
-        {
-                if (ret == 1)
-                        /* ret != 0 only if we get interrupted -arca */
-                        ret = 0;
-                break;
-        }
-        schedule();
-        DOWN_TAIL(TASK_INTERRUPTIBLE)
-        return ret;
-}
-int __down_trylock(struct semaphore * sem)
-{
-        return waking_non_zero_trylock(sem);
-}
diff --git a/arch/sh/kernel/sh_ksyms_32.c b/arch/sh/kernel/sh_ksyms_32.c
index 45bb333fd9ec..6d405462cee8 100644
--- a/arch/sh/kernel/sh_ksyms_32.c
+++ b/arch/sh/kernel/sh_ksyms_32.c
@@ -9,7 +9,6 @@
 #include <linux/pci.h>
 #include <linux/irq.h>
 #include <asm/sections.h>
-#include <asm/semaphore.h>
 #include <asm/processor.h>
 #include <asm/uaccess.h>
 #include <asm/checksum.h>
@@ -48,12 +47,6 @@ EXPORT_SYMBOL(__copy_user);
 EXPORT_SYMBOL(get_vm_area);
 #endif
-/* semaphore exports */
-EXPORT_SYMBOL(__up);
-EXPORT_SYMBOL(__down);
-EXPORT_SYMBOL(__down_interruptible);
-EXPORT_SYMBOL(__down_trylock);
 EXPORT_SYMBOL(__udelay);
 EXPORT_SYMBOL(__ndelay);
 EXPORT_SYMBOL(__const_udelay);
diff --git a/arch/sh/kernel/sh_ksyms_64.c b/arch/sh/kernel/sh_ksyms_64.c
index b6410ce4bd1d..a310c9707f03 100644
--- a/arch/sh/kernel/sh_ksyms_64.c
+++ b/arch/sh/kernel/sh_ksyms_64.c
@@ -16,7 +16,6 @@
 #include <linux/in6.h>
 #include <linux/interrupt.h>
 #include <linux/screen_info.h>
-#include <asm/semaphore.h>
 #include <asm/processor.h>
 #include <asm/uaccess.h>
 #include <asm/checksum.h>
@@ -37,9 +36,6 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
 EXPORT_SYMBOL(screen_info);
 #endif
-EXPORT_SYMBOL(__down);
-EXPORT_SYMBOL(__down_trylock);
-EXPORT_SYMBOL(__up);
 EXPORT_SYMBOL(__put_user_asm_l);
 EXPORT_SYMBOL(__get_user_asm_l);
 EXPORT_SYMBOL(copy_page);
author	Matthew Wilcox <matthew@wil.cx>	2008-03-07 21:55:58 -0500
committer	Matthew Wilcox <willy@linux.intel.com>	2008-04-17 10:42:34 -0400
commit	64ac24e738823161693bf791f87adc802cf529ff (patch)
tree	19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/sh
parent	e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)

diff --git a/arch/sh/kernel/Makefile_32 b/arch/sh/kernel/Makefile_32 index 62bf373266f7..4bbdce36b92b 100644 --- a/arch/sh/kernel/Makefile_32 +++ b/arch/sh/kernel/Makefile_32
@@ -5,7 +5,7 @@
5	extra-y := head_32.o init_task.o vmlinux.lds	5	extra-y := head_32.o init_task.o vmlinux.lds
6		6
7	obj-y := debugtraps.o io.o io_generic.o irq.o machvec.o process_32.o \	7	obj-y := debugtraps.o io.o io_generic.o irq.o machvec.o process_32.o \
8	ptrace_32.o semaphore.o setup.o signal_32.o sys_sh.o sys_sh32.o \	8	ptrace_32.o setup.o signal_32.o sys_sh.o sys_sh32.o \
9	syscalls_32.o time_32.o topology.o traps.o traps_32.o	9	syscalls_32.o time_32.o topology.o traps.o traps_32.o
10		10
11	obj-y += cpu/ timers/	11	obj-y += cpu/ timers/


diff --git a/arch/sh/kernel/Makefile_64 b/arch/sh/kernel/Makefile_64 index e01283d49cbf..6edf53b93d94 100644 --- a/arch/sh/kernel/Makefile_64 +++ b/arch/sh/kernel/Makefile_64
@@ -1,7 +1,7 @@
1	extra-y := head_64.o init_task.o vmlinux.lds	1	extra-y := head_64.o init_task.o vmlinux.lds
2		2
3	obj-y := debugtraps.o io.o io_generic.o irq.o machvec.o process_64.o \	3	obj-y := debugtraps.o io.o io_generic.o irq.o machvec.o process_64.o \
4	ptrace_64.o semaphore.o setup.o signal_64.o sys_sh.o sys_sh64.o \	4	ptrace_64.o setup.o signal_64.o sys_sh.o sys_sh64.o \
5	syscalls_64.o time_64.o topology.o traps.o traps_64.o	5	syscalls_64.o time_64.o topology.o traps.o traps_64.o
6		6
7	obj-y += cpu/ timers/	7	obj-y += cpu/ timers/


diff --git a/arch/sh/kernel/semaphore.c b/arch/sh/kernel/semaphore.c deleted file mode 100644 index 184119eeae56..000000000000 --- a/arch/sh/kernel/semaphore.c +++ /dev/null
@@ -1,139 +0,0 @@
1	/*
2	* Just taken from alpha implementation.
3	* This can't work well, perhaps.
4	*/
5	/*
6	* Generic semaphore code. Buyer beware. Do your own
7	* specific changes in <asm/semaphore-helper.h>
8	*/
9
10	#include <linux/errno.h>
11	#include <linux/sched.h>
12	#include <linux/wait.h>
13	#include <linux/init.h>
14	#include <asm/semaphore.h>
15	#include <asm/semaphore-helper.h>
16
17	DEFINE_SPINLOCK(semaphore_wake_lock);
18
19	/*
20	* Semaphores are implemented using a two-way counter:
21	* The "count" variable is decremented for each process
22	* that tries to sleep, while the "waking" variable is
23	* incremented when the "up()" code goes to wake up waiting
24	* processes.
25	*
26	* Notably, the inline "up()" and "down()" functions can
27	* efficiently test if they need to do any extra work (up
28	* needs to do something only if count was negative before
29	* the increment operation.
30	*
31	* waking_non_zero() (from asm/semaphore.h) must execute
32	* atomically.
33	*
34	* When __up() is called, the count was negative before
35	* incrementing it, and we need to wake up somebody.
36	*
37	* This routine adds one to the count of processes that need to
38	* wake up and exit. ALL waiting processes actually wake up but
39	* only the one that gets to the "waking" field first will gate
40	* through and acquire the semaphore. The others will go back
41	* to sleep.
42	*
43	* Note that these functions are only called when there is
44	* contention on the lock, and as such all this is the
45	* "non-critical" part of the whole semaphore business. The
46	* critical part is the inline stuff in <asm/semaphore.h>
47	* where we want to avoid any extra jumps and calls.
48	*/
49	void __up(struct semaphore *sem)
50	{
51	wake_one_more(sem);
52	wake_up(&sem->wait);
53	}
54
55	/*
56	* Perform the "down" function. Return zero for semaphore acquired,
57	* return negative for signalled out of the function.
58	*
59	* If called from __down, the return is ignored and the wait loop is
60	* not interruptible. This means that a task waiting on a semaphore
61	* using "down()" cannot be killed until someone does an "up()" on
62	* the semaphore.
63	*
64	* If called from __down_interruptible, the return value gets checked
65	* upon return. If the return value is negative then the task continues
66	* with the negative value in the return register (it can be tested by
67	* the caller).
68	*
69	* Either form may be used in conjunction with "up()".
70	*
71	*/
72
73	#define DOWN_VAR \
74	struct task_struct *tsk = current; \
75	wait_queue_t wait; \
76	init_waitqueue_entry(&wait, tsk);
77
78	#define DOWN_HEAD(task_state) \
79	\
80	\
81	tsk->state = (task_state); \
82	add_wait_queue(&sem->wait, &wait); \
83	\
84	/* \
85	* Ok, we're set up. sem->count is known to be less than zero \
86	* so we must wait. \
87	* \
88	* We can let go the lock for purposes of waiting. \
89	* We re-acquire it after awaking so as to protect \
90	* all semaphore operations. \
91	* \
92	* If "up()" is called before we call waking_non_zero() then \
93	* we will catch it right away. If it is called later then \
94	* we will have to go through a wakeup cycle to catch it. \
95	* \
96	* Multiple waiters contend for the semaphore lock to see \
97	* who gets to gate through and who has to wait some more. \
98	*/ \
99	for (;;) {
100
101	#define DOWN_TAIL(task_state) \
102	tsk->state = (task_state); \
103	} \
104	tsk->state = TASK_RUNNING; \
105	remove_wait_queue(&sem->wait, &wait);
106
107	void __sched __down(struct semaphore * sem)
108	{
109	DOWN_VAR
110	DOWN_HEAD(TASK_UNINTERRUPTIBLE)
111	if (waking_non_zero(sem))
112	break;
113	schedule();
114	DOWN_TAIL(TASK_UNINTERRUPTIBLE)
115	}
116
117	int __sched __down_interruptible(struct semaphore * sem)
118	{
119	int ret = 0;
120	DOWN_VAR
121	DOWN_HEAD(TASK_INTERRUPTIBLE)
122
123	ret = waking_non_zero_interruptible(sem, tsk);
124	if (ret)
125	{
126	if (ret == 1)
127	/* ret != 0 only if we get interrupted -arca */
128	ret = 0;
129	break;
130	}
131	schedule();
132	DOWN_TAIL(TASK_INTERRUPTIBLE)
133	return ret;
134	}
135
136	int __down_trylock(struct semaphore * sem)
137	{
138	return waking_non_zero_trylock(sem);
139	}


diff --git a/arch/sh/kernel/sh_ksyms_32.c b/arch/sh/kernel/sh_ksyms_32.c index 45bb333fd9ec..6d405462cee8 100644 --- a/arch/sh/kernel/sh_ksyms_32.c +++ b/arch/sh/kernel/sh_ksyms_32.c
@@ -9,7 +9,6 @@
9	#include <linux/pci.h>	9	#include <linux/pci.h>
10	#include <linux/irq.h>	10	#include <linux/irq.h>
11	#include <asm/sections.h>	11	#include <asm/sections.h>
12	#include <asm/semaphore.h>
13	#include <asm/processor.h>	12	#include <asm/processor.h>
14	#include <asm/uaccess.h>	13	#include <asm/uaccess.h>
15	#include <asm/checksum.h>	14	#include <asm/checksum.h>
@@ -48,12 +47,6 @@ EXPORT_SYMBOL(__copy_user);
48	EXPORT_SYMBOL(get_vm_area);	47	EXPORT_SYMBOL(get_vm_area);
49	#endif	48	#endif
50		49
51	/* semaphore exports */
52	EXPORT_SYMBOL(__up);
53	EXPORT_SYMBOL(__down);
54	EXPORT_SYMBOL(__down_interruptible);
55	EXPORT_SYMBOL(__down_trylock);
56
57	EXPORT_SYMBOL(__udelay);	50	EXPORT_SYMBOL(__udelay);
58	EXPORT_SYMBOL(__ndelay);	51	EXPORT_SYMBOL(__ndelay);
59	EXPORT_SYMBOL(__const_udelay);	52	EXPORT_SYMBOL(__const_udelay);


diff --git a/arch/sh/kernel/sh_ksyms_64.c b/arch/sh/kernel/sh_ksyms_64.c index b6410ce4bd1d..a310c9707f03 100644 --- a/arch/sh/kernel/sh_ksyms_64.c +++ b/arch/sh/kernel/sh_ksyms_64.c
@@ -16,7 +16,6 @@
16	#include <linux/in6.h>	16	#include <linux/in6.h>
17	#include <linux/interrupt.h>	17	#include <linux/interrupt.h>
18	#include <linux/screen_info.h>	18	#include <linux/screen_info.h>
19	#include <asm/semaphore.h>
20	#include <asm/processor.h>	19	#include <asm/processor.h>
21	#include <asm/uaccess.h>	20	#include <asm/uaccess.h>
22	#include <asm/checksum.h>	21	#include <asm/checksum.h>
@@ -37,9 +36,6 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
37	EXPORT_SYMBOL(screen_info);	36	EXPORT_SYMBOL(screen_info);
38	#endif	37	#endif
39		38
40	EXPORT_SYMBOL(__down);
41	EXPORT_SYMBOL(__down_trylock);
42	EXPORT_SYMBOL(__up);
43	EXPORT_SYMBOL(__put_user_asm_l);	39	EXPORT_SYMBOL(__put_user_asm_l);
44	EXPORT_SYMBOL(__get_user_asm_l);	40	EXPORT_SYMBOL(__get_user_asm_l);
45	EXPORT_SYMBOL(copy_page);	41	EXPORT_SYMBOL(copy_page);