diff options
author | Matthew Wilcox <matthew@wil.cx> | 2008-03-08 02:55:58 (GMT) |
---|---|---|
committer | Matthew Wilcox <willy@linux.intel.com> | 2008-04-17 14:42:34 (GMT) |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/sh/kernel | |
parent | e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff) | |
download | linux-64ac24e738823161693bf791f87adc802cf529ff.tar.xz |
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/sh/kernel')
-rw-r--r-- | arch/sh/kernel/Makefile_32 | 2 | ||||
-rw-r--r-- | arch/sh/kernel/Makefile_64 | 2 | ||||
-rw-r--r-- | arch/sh/kernel/semaphore.c | 139 | ||||
-rw-r--r-- | arch/sh/kernel/sh_ksyms_32.c | 7 | ||||
-rw-r--r-- | arch/sh/kernel/sh_ksyms_64.c | 4 |
5 files changed, 2 insertions, 152 deletions
diff --git a/arch/sh/kernel/Makefile_32 b/arch/sh/kernel/Makefile_32 index 62bf373..4bbdce3 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 e01283d..6edf53b 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 184119e..0000000 --- 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 45bb333..6d40546 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 b6410ce..a310c97 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); |