+++ /dev/null
-/*
- * arch/ubicom32/kernel/semaphore.c
- * Ubicom32 architecture semaphore implementation.
- *
- * (C) Copyright 2009, Ubicom, Inc.
- *
- * This file is part of the Ubicom32 Linux Kernel Port.
- *
- * The Ubicom32 Linux Kernel Port is free software: you can redistribute
- * it and/or modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 2 of the
- * License, or (at your option) any later version.
- *
- * The Ubicom32 Linux Kernel Port is distributed in the hope that it
- * will be useful, but WITHOUT ANY WARRANTY; without even the implied
- * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
- * the GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with the Ubicom32 Linux Kernel Port. If not,
- * see <http://www.gnu.org/licenses/>.
- *
- * Ubicom32 implementation derived from (with many thanks):
- * arch/m68knommu
- * arch/blackfin
- * arch/parisc
- */
-/*
- * 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);
-}
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