+++ /dev/null
-/*!
- * \file
- * <!--
- * Copyright 2001, 2004 Develer S.r.l. (http://www.develer.com/)
- * Copyright 1999, 2000, 2001 Bernardo Innocenti <bernie@develer.com>
- * This file is part of DevLib - See devlib/README for information.
- * -->
- *
- * \brief Semaphore based synchronization services.
- *
- * \version $Id$
- *
- * \author Bernardo Innocenti <bernie@develer.com>
- */
-
-/*#*
- *#* $Log$
- *#* Revision 1.6 2004/10/21 10:57:21 bernie
- *#* Use proc_forbid()/proc_permit().
- *#*
- *#* Revision 1.5 2004/10/21 10:48:57 bernie
- *#* sem_release(): Simplify (made by rasky on scfirm).
- *#*
- *#* Revision 1.4 2004/08/25 14:12:09 rasky
- *#* Aggiornato il comment block dei log RCS
- *#*
- *#* Revision 1.3 2004/08/08 05:53:23 bernie
- *#* Use DISABLE_IRQSAVE/ENABLE_IRQRESTORE; Cleanup documentation.
- *#*
- *#* Revision 1.2 2004/06/03 11:27:09 bernie
- *#* Add dual-license information.
- *#*
- *#* Revision 1.1 2004/05/23 17:27:00 bernie
- *#* Import kern/ subdirectory.
- *#*/
-
-#include "sem.h"
-#include "proc.h"
-#include "proc_p.h"
-#include "signal.h"
-#include "hw.h"
-
-
-/*!
- * \brief Initialize a Semaphore structure.
- */
-void sem_init(struct Semaphore *s)
-{
- INITLIST(&s->wait_queue);
- s->owner = NULL;
- s->nest_count = 0;
-}
-
-
-/*!
- * \brief Attempt to lock a semaphore without waiting.
- *
- * \return true in case of success, false if the semaphore
- * was already locked by someone else.
- *
- * \note each call to sem_attempt() must be matched by a
- * call to sem_release().
- *
- * \see sem_obtain() sem_release()
- */
-bool sem_attempt(struct Semaphore *s)
-{
- bool result = false;
-
- proc_forbid();
- if ((!s->owner) || (s->owner == CurrentProcess))
- {
- s->owner = CurrentProcess;
- s->nest_count++;
- result = true;
- }
- proc_permit();
-
- return result;
-}
-
-
-/*!
- * \brief Lock a semaphore.
- *
- * If the semaphore is already owned by another process, the caller
- * process will be enqueued into the waiting list and sleep until
- * the semaphore is available.
- *
- * \note Each call to sem_obtain() must be matched by a
- * call to sem_release().
- *
- * \note This routine is optimized for highest speed in
- * the most common case: the semaphore is free or locked
- * by the calling process itself. Rearranging this code
- * is probably a bad idea.
- *
- * \sa sem_release() sem_attempt()
- */
-void sem_obtain(struct Semaphore *s)
-{
- proc_forbid();
-
- /* Is the semaphore already locked by another process? */
- if (UNLIKELY(s->owner && (s->owner != CurrentProcess)))
- {
- /* Append calling process to the wait queue */
- ADDTAIL(&s->wait_queue, (Node *)CurrentProcess);
-
- /*
- * We will wake up only when the current owner calls
- * sem_release(). Then, the semaphore will already
- * be locked for us.
- */
- proc_permit();
- proc_schedule();
- }
- else
- {
- /* The semaphore was free: lock it */
- s->owner = CurrentProcess;
- s->nest_count++;
- proc_permit();
- }
-}
-
-
-/*!
- * \brief Release a lock on a previously locked semaphore.
- *
- * If the nesting count of the semaphore reaches zero,
- * the next process waiting for it will be awaken.
- *
- * \note This routine is optimized for highest speed in
- * the most common case: the semaphore has been locked just
- * once and nobody else was waiting for it. Rearranging
- * this code is probably a bad idea.
- *
- * \sa sem_obtain() sem_attempt()
- */
-void sem_release(struct Semaphore *s)
-{
- proc_forbid();
-
- /*
- * Decrement nesting count and check if the semaphore
- * has been fully unlocked.
- */
- if (--s->nest_count == 0)
- {
- Process *proc;
-
- /* Disown semaphore */
- s->owner = NULL;
-
- /* Give semaphore to the first applicant, if any */
- if (UNLIKELY((proc = (Process *)REMHEAD(&s->wait_queue))))
- {
- s->nest_count = 1;
- s->owner = proc;
- SCHED_ENQUEUE(proc);
- }
- }
-
- proc_permit();
-}