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Diffstat (limited to 'nuttx/sched/sem_waitirq.c')
-rw-r--r-- | nuttx/sched/sem_waitirq.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/nuttx/sched/sem_waitirq.c b/nuttx/sched/sem_waitirq.c new file mode 100644 index 000000000..3d3af18de --- /dev/null +++ b/nuttx/sched/sem_waitirq.c @@ -0,0 +1,145 @@ +/**************************************************************************** + * sched/sem_waitirq.c + * + * Copyright (C) 2007-2010 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 <sched.h> +#include <errno.h> +#include <nuttx/arch.h> + +#include "sem_internal.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Type Declarations + ****************************************************************************/ + +/**************************************************************************** + * Global Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: sem_waitirq + * + * Description: + * This function is called when a signal is received by a task that is + * waiting on a semaphore. According to the POSIX spec, "...the calling + * thread shall not return from the call to [sem_wait] until it either + * locks the semaphore or the call is interrupted by a signal." + * + * Parameters: + * wtcb - A pointer to the TCB of the task that is waiting on a + * semphaphore, but has received a signal or timeout instead. + * errcode - EINTR if the semaphore wait was awakened by a signal; + * ETIMEDOUT if awakened by a timeout + * + * Return Value: + * None + * + * Assumptions: + * + ****************************************************************************/ + +void sem_waitirq(FAR _TCB *wtcb, int errcode) +{ + irqstate_t saved_state; + + /* Disable interrupts. This is necessary (unfortunately) because an + * interrupt handler may attempt to post the semaphore while we are + * doing this. + */ + + saved_state = irqsave(); + + /* It is possible that an interrupt/context switch beat us to the punch + * and already changed the task's state. + */ + + if (wtcb->task_state == TSTATE_WAIT_SEM) + { + sem_t *sem = wtcb->waitsem; + DEBUGASSERT(sem != NULL && sem->semcount < 0); + + /* Restore the correct priority of all threads that hold references + * to this semaphore. + */ + + sem_canceled(wtcb, sem); + + /* And increment the count on the semaphore. This releases the count + * that was taken by sem_post(). This count decremented the semaphore + * count to negative and caused the thread to be blocked in the first + * place. + */ + + sem->semcount++; + + /* Indicate that the semaphore wait is over. */ + + wtcb->waitsem = NULL; + + /* Mark the errno value for the thread. */ + + wtcb->pterrno = errcode; + + /* Restart the task. */ + + up_unblock_task(wtcb); + } + + /* Interrupts may now be enabled. */ + + irqrestore(saved_state); +} + |