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author | 2008-03-07 21:55:58 -0500 | |
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committer | 2008-04-17 10:42:34 -0400 | |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/m68knommu/kernel | |
parent | Add semaphore.h to kernel_lock.c (diff) | |
download | linux-64ac24e738823161693bf791f87adc802cf529ff.tar.gz linux-64ac24e738823161693bf791f87adc802cf529ff.tar.bz2 linux-64ac24e738823161693bf791f87adc802cf529ff.zip |
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/kernel')
-rw-r--r-- | arch/m68knommu/kernel/Makefile | 2 | ||||
-rw-r--r-- | arch/m68knommu/kernel/m68k_ksyms.c | 6 | ||||
-rw-r--r-- | arch/m68knommu/kernel/semaphore.c | 133 |
3 files changed, 1 insertions, 140 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 @@ extra-y := vmlinux.lds obj-y += dma.o entry.o init_task.o irq.o m68k_ksyms.o process.o ptrace.o \ - semaphore.o setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o + setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o obj-$(CONFIG_MODULES) += module.o obj-$(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 @@ #include <asm/pgalloc.h> #include <asm/irq.h> #include <asm/io.h> -#include <asm/semaphore.h> #include <asm/checksum.h> #include <asm/current.h> @@ -39,11 +38,6 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck); EXPORT_SYMBOL(memcpy); EXPORT_SYMBOL(memset); -EXPORT_SYMBOL(__down_failed); -EXPORT_SYMBOL(__down_failed_interruptible); -EXPORT_SYMBOL(__down_failed_trylock); -EXPORT_SYMBOL(__up_wakeup); - /* * libgcc functions - functions that are used internally by the * 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 @@ -/* - * Generic semaphore code. Buyer beware. Do your own - * specific changes in <asm/semaphore-helper.h> - */ - -#include <linux/sched.h> -#include <linux/err.h> -#include <linux/init.h> -#include <asm/semaphore-helper.h> - -#ifndef CONFIG_RMW_INSNS -spinlock_t semaphore_wake_lock; -#endif - -/* - * 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_HEAD(task_state) \ - \ - \ - current->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) \ - current->state = (task_state); \ - } \ - current->state = TASK_RUNNING; \ - remove_wait_queue(&sem->wait, &wait); - -void __sched __down(struct semaphore * sem) -{ - DECLARE_WAITQUEUE(wait, current); - - DOWN_HEAD(TASK_UNINTERRUPTIBLE) - if (waking_non_zero(sem)) - break; - schedule(); - DOWN_TAIL(TASK_UNINTERRUPTIBLE) -} - -int __sched __down_interruptible(struct semaphore * sem) -{ - DECLARE_WAITQUEUE(wait, current); - int ret = 0; - - DOWN_HEAD(TASK_INTERRUPTIBLE) - - ret = waking_non_zero_interruptible(sem, current); - 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); -} |