3dca5eba15
- Remove per-thread errno from the TCB structure (pterrno) - Remove get_errno() and set_errno() as functions. The macros are still available as stubs and will be needed in the future if we need to access the errno from a different address environment (KERNEL mode). - Add errno value to the tls_info_s structure definitions - Move sched/errno to libs/libc/errno. Replace old TCB access to the errno with TLS access to the errno.
286 lines
8.6 KiB
C
286 lines
8.6 KiB
C
/****************************************************************************
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* sched/semaphore/sem_wait.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <assert.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/cancelpt.h>
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#include "sched/sched.h"
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#include "semaphore/semaphore.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxsem_wait
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*
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* Description:
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* This function attempts to lock the semaphore referenced by 'sem'. If
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* the semaphore value is (<=) zero, then the calling task will not return
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* until it successfully acquires the lock.
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*
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* This is an internal OS interface. It is functionally equivalent to
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* sem_wait except that:
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*
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* - It is not a cancellation point, and
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* - It does not modify the errno value.
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*
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* Input Parameters:
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* sem - Semaphore descriptor.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* Possible returned errors:
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*
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* - EINVAL: Invalid attempt to get the semaphore
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* - EINTR: The wait was interrupted by the receipt of a signal.
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*
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****************************************************************************/
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int nxsem_wait(FAR sem_t *sem)
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{
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FAR struct tcb_s *rtcb = this_task();
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irqstate_t flags;
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int ret = -EINVAL;
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/* This API should not be called from interrupt handlers */
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DEBUGASSERT(sem != NULL && up_interrupt_context() == false);
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/* The following operations must be performed with interrupts
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* disabled because nxsem_post() may be called from an interrupt
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* handler.
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*/
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flags = enter_critical_section();
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/* Make sure we were supplied with a valid semaphore. */
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if (sem != NULL)
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{
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/* Check if the lock is available */
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if (sem->semcount > 0)
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{
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/* It is, let the task take the semaphore. */
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sem->semcount--;
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nxsem_addholder(sem);
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rtcb->waitsem = NULL;
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ret = OK;
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}
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/* The semaphore is NOT available, We will have to block the
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* current thread of execution.
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*/
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else
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{
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/* First, verify that the task is not already waiting on a
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* semaphore
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*/
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DEBUGASSERT(rtcb->waitsem == NULL);
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/* Handle the POSIX semaphore (but don't set the owner yet) */
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sem->semcount--;
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/* Save the waited on semaphore in the TCB */
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rtcb->waitsem = sem;
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/* If priority inheritance is enabled, then check the priority of
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* the holder of the semaphore.
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*/
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Disable context switching. The following operations must be
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* atomic with regard to the scheduler.
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*/
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sched_lock();
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/* Boost the priority of any threads holding a count on the
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* semaphore.
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*/
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nxsem_boostpriority(sem);
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#endif
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/* Set the errno value to zero (preserving the original errno)
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* value). We reuse the per-thread errno to pass information
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* between sem_waitirq() and this functions.
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*/
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rtcb->errcode = OK;
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/* Add the TCB to the prioritized semaphore wait queue, after
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* checking this is not the idle task - descheduling that
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* isn't going to end well.
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*/
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DEBUGASSERT(NULL != rtcb->flink);
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up_block_task(rtcb, TSTATE_WAIT_SEM);
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/* When we resume at this point, either (1) the semaphore has been
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* assigned to this thread of execution, or (2) the semaphore wait
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* has been interrupted by a signal or a timeout. We can detect
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* these latter cases be examining the per-thread errno value.
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*
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* In the event that the semaphore wait was interrupted by a
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* signal or a timeout, certain semaphore clean-up operations have
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* already been performed (see sem_waitirq.c). Specifically:
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*
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* - nxsem_canceled() was called to restore the priority of all
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* threads that hold a reference to the semaphore,
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* - The semaphore count was decremented, and
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* - tcb->waitsem was nullifed.
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*
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* It is necessary to do these things in sem_waitirq.c because a
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* long time may elapse between the time that the signal was issued
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* and this thread is awakened and this leaves a door open to
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* several race conditions.
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*/
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/* Check if an error occurred while we were sleeping. Expected
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* errors include EINTR meaning that we were awakened by a signal
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* or ETIMEDOUT meaning that the timer expired for the case of
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* sem_timedwait().
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*
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* If we were not awakened by a signal or a timeout, then
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* nxsem_addholder() was called by logic in sem_wait() fore this
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* thread was restarted.
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*/
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ret = rtcb->errcode != OK ? -rtcb->errcode : OK;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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sched_unlock();
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#endif
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}
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}
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leave_critical_section(flags);
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return ret;
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}
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/****************************************************************************
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* Name: nxsem_wait_uninterruptible
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*
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* Description:
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* This function is wrapped version of nxsem_wait(), which is
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* uninterruptible and convenient for use.
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*
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* Parameters:
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* sem - Semaphore descriptor.
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*
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* Return Value:
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* Zero(OK) - On success
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* EINVAL - Invalid attempt to get the semaphore
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* ECANCELED - May be returned if the thread is canceled while waiting.
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*
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****************************************************************************/
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int nxsem_wait_uninterruptible(FAR sem_t *sem)
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{
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int ret;
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do
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{
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/* Take the semaphore (perhaps waiting) */
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ret = nxsem_wait(sem);
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}
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while (ret == -EINTR);
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return ret;
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}
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/****************************************************************************
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* Name: sem_wait
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*
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* Description:
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* This function attempts to lock the semaphore referenced by 'sem'. If
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* the semaphore value is (<=) zero, then the calling task will not return
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* until it successfully acquires the lock.
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*
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* Input Parameters:
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* sem - Semaphore descriptor.
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*
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* Returned Value:
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* This function is a standard, POSIX application interface. It returns
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* zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
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* the errno value is set appropriately. Possible errno values include:
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*
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* - EINVAL: Invalid attempt to get the semaphore
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* - EINTR: The wait was interrupted by the receipt of a signal.
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*
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****************************************************************************/
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int sem_wait(FAR sem_t *sem)
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{
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int errcode;
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int ret;
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/* sem_wait() is a cancellation point */
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if (enter_cancellation_point())
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{
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#ifdef CONFIG_CANCELLATION_POINTS
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/* If there is a pending cancellation, then do not perform
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* the wait. Exit now with ECANCELED.
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*/
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errcode = ECANCELED;
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goto errout_with_cancelpt;
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#endif
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}
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/* Let nxsem_wait() do the real work */
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ret = nxsem_wait(sem);
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if (ret < 0)
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{
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errcode = -ret;
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goto errout_with_cancelpt;
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}
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leave_cancellation_point();
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return OK;
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errout_with_cancelpt:
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set_errno(errcode);
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leave_cancellation_point();
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return ERROR;
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}
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