109 lines
2.7 KiB
C
109 lines
2.7 KiB
C
/*
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* linux/arch/s390/kernel/semaphore.c
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*
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* S390 version
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* Copyright (C) 1998-2000 IBM Corporation
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* Author(s): Martin Schwidefsky
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*
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* Derived from "linux/arch/i386/kernel/semaphore.c
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* Copyright (C) 1999, Linus Torvalds
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*
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*/
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#include <linux/sched.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <asm/semaphore.h>
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/*
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* Atomically update sem->count. Equivalent to:
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* old_val = sem->count.counter;
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* new_val = ((old_val >= 0) ? old_val : 0) + incr;
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* sem->count.counter = new_val;
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* return old_val;
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*/
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static inline int __sem_update_count(struct semaphore *sem, int incr)
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{
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int old_val, new_val;
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asm volatile(
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" l %0,0(%3)\n"
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"0: ltr %1,%0\n"
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" jhe 1f\n"
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" lhi %1,0\n"
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"1: ar %1,%4\n"
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" cs %0,%1,0(%3)\n"
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" jl 0b\n"
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: "=&d" (old_val), "=&d" (new_val), "=m" (sem->count)
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: "a" (&sem->count), "d" (incr), "m" (sem->count)
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: "cc");
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return old_val;
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}
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/*
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* The inline function up() incremented count but the result
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* was <= 0. This indicates that some process is waiting on
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* the semaphore. The semaphore is free and we'll wake the
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* first sleeping process, so we set count to 1 unless some
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* other cpu has called up in the meantime in which case
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* we just increment count by 1.
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*/
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void __up(struct semaphore *sem)
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{
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__sem_update_count(sem, 1);
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wake_up(&sem->wait);
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}
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/*
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* The inline function down() decremented count and the result
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* was < 0. The wait loop will atomically test and update the
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* semaphore counter following the rules:
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* count > 0: decrement count, wake up queue and exit.
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* count <= 0: set count to -1, go to sleep.
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*/
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void __sched __down(struct semaphore * sem)
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{
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struct task_struct *tsk = current;
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DECLARE_WAITQUEUE(wait, tsk);
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__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
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add_wait_queue_exclusive(&sem->wait, &wait);
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while (__sem_update_count(sem, -1) <= 0) {
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schedule();
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set_task_state(tsk, TASK_UNINTERRUPTIBLE);
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}
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remove_wait_queue(&sem->wait, &wait);
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__set_task_state(tsk, TASK_RUNNING);
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wake_up(&sem->wait);
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}
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/*
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* Same as __down() with an additional test for signals.
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* If a signal is pending the count is updated as follows:
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* count > 0: wake up queue and exit.
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* count <= 0: set count to 0, wake up queue and exit.
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*/
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int __sched __down_interruptible(struct semaphore * sem)
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{
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int retval = 0;
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struct task_struct *tsk = current;
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DECLARE_WAITQUEUE(wait, tsk);
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__set_task_state(tsk, TASK_INTERRUPTIBLE);
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add_wait_queue_exclusive(&sem->wait, &wait);
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while (__sem_update_count(sem, -1) <= 0) {
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if (signal_pending(current)) {
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__sem_update_count(sem, 0);
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retval = -EINTR;
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break;
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}
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schedule();
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set_task_state(tsk, TASK_INTERRUPTIBLE);
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}
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remove_wait_queue(&sem->wait, &wait);
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__set_task_state(tsk, TASK_RUNNING);
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wake_up(&sem->wait);
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return retval;
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}
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