Resync new repository with old repo r5166

git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5153 42af7a65-404d-4744-a932-0658087f49c3
2026-10-31 00:11:36 +08:00 · 2012-09-17 18:18:44 +00:00
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+/****************************************************************************
+ * sched/sem_wait.c
+ *
+ *   Copyright (C) 2007-2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdbool.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <assert.h>
+#include <nuttx/arch.h>
+
+#include "os_internal.h"
+#include "sem_internal.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sem_wait
+ *
+ * Description:
+ *   This function attempts to lock the semaphore referenced by 'sem'.  If
+ *   the semaphore value is (<=) zero, then the calling task will not return
+ *   until it successfully acquires the lock.
+ *
+ * Parameters:
+ *   sem - Semaphore descriptor.
+ *
+ * Return Value:
+ *   0 (OK), or -1 (ERROR) is unsuccessful
+ *   If this function returns -1 (ERROR), then the cause of the failure will
+ *   be reported in 'errno' as:
+ *   - EINVAL:  Invalid attempt to get the semaphore
+ *   - EINTR:   The wait was interrupted by the receipt of a signal.
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int sem_wait(FAR sem_t *sem)
+{
+  FAR _TCB  *rtcb = (FAR _TCB*)g_readytorun.head;
+  int        ret  = ERROR;
+  irqstate_t saved_state;
+
+  /* This API should not be called from interrupt handlers */
+
+  DEBUGASSERT(up_interrupt_context() == false)
+
+  /* Assume any errors reported are due to invalid arguments. */
+
+  errno = EINVAL;
+
+  if (sem)
+    {
+      /* The following operations must be performed with interrupts
+       * disabled because sem_post() may be called from an interrupt
+       * handler.
+       */
+
+      saved_state = irqsave();
+
+      /* Check if the lock is available */
+
+      if (sem->semcount > 0)
+        {
+          /* It is, let the task take the semaphore. */
+
+          sem->semcount--;
+          sem_addholder(sem);
+          rtcb->waitsem = NULL;
+          ret = OK;
+        }
+
+      /* The semaphore is NOT available, We will have to block the
+       * current thread of execution.
+       */
+
+      else
+        {
+          /* First, verify that the task is not already waiting on a
+           * semaphore
+           */
+
+          if (rtcb->waitsem != NULL)
+            {
+              PANIC(OSERR_BADWAITSEM);
+            }
+
+          /* Handle the POSIX semaphore (but don't set the owner yet) */
+
+          sem->semcount--;
+
+          /* Save the waited on semaphore in the TCB */
+
+          rtcb->waitsem = sem;
+
+          /* If priority inheritance is enabled, then check the priority of
+           * the holder of the semaphore.
+           */
+
+#ifdef CONFIG_PRIORITY_INHERITANCE
+          /* Disable context switching.  The following operations must be
+           * atomic with regard to the scheduler.
+           */
+
+          sched_lock();
+
+          /* Boost the priority of any threads holding a count on the
+           * semaphore.
+           */
+
+          sem_boostpriority(sem);
+#endif
+          /* Add the TCB to the prioritized semaphore wait queue */
+
+          errno = 0;
+          up_block_task(rtcb, TSTATE_WAIT_SEM);
+
+          /* When we resume at this point, either (1) the semaphore has been
+           * assigned to this thread of execution, or (2) the semaphore wait
+           * has been interrupted by a signal or a timeout.  We can detect these
+           * latter cases be examining the errno value.
+           *
+           * In the event that the semaphore wait was interrupted by a signal or
+           * a timeout, certain semaphore clean-up operations have already been
+           * performed (see sem_waitirq.c).  Specifically:
+           *
+           * - sem_canceled() was called to restore the priority of all threads
+           *   that hold a reference to the semaphore,
+           * - The semaphore count was decremented, and
+           * - tcb->waitsem was nullifed.
+           *
+           * It is necesaary to do these things in sem_waitirq.c because a long
+           * time may elapse between the time that the signal was issued and
+           * this thread is awakened and this leaves a door open to several
+           * race conditions.
+           */
+
+          if (errno != EINTR && errno != ETIMEDOUT)
+            {
+              /* Not awakened by a signal or a timeout... We hold the semaphore */
+
+              sem_addholder(sem);
+              ret = OK;
+            }
+
+#ifdef CONFIG_PRIORITY_INHERITANCE
+          sched_unlock();
+#endif
+        }
+
+      /* Interrupts may now be enabled. */
+
+      irqrestore(saved_state);
+    }
+
+  return ret;
+}