126 lines
4.8 KiB
C
126 lines
4.8 KiB
C
/****************************************************************************
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* sched/errno/errno_getptr.c
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*
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* Copyright (C) 2007, 2008, 2011, 2014 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 <sched.h>
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#include <errno.h>
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#include <nuttx/arch.h>
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#include "sched/sched.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#undef get_errno_ptr
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#undef errno
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/* This is a 'dummy' errno value to use in context where there is no valid
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* errno location to use. For example, when running from an interrupt handler
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* or early in initialization when task structures have not yet been
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* initialized.
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*/
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static int g_irqerrno;
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: get_errno_ptr
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*
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* Description:
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* Return a pointer to the thread specific errno.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* A pointer to the per-thread errno variable.
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*
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* Assumptions:
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*
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****************************************************************************/
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FAR int *get_errno_ptr(void)
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{
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/* Check if this function was called from an interrupt handler. In that
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* case, we have to do things a little differently to prevent the interrupt
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* handler from modifying the tasks errno value.
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*/
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if (!up_interrupt_context())
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{
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/* We were called from the normal tasking context. Verify that the
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* task at the head of the ready-to-run list is actually running. It
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* may not be running during very brief times during context switching
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* logic (see, for example, task_exit.c).
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*
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* There is also a corner case early in the initialization sequence:
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* The ready to run list may not yet be initialized and this_task()
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* may be NULL.
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*/
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FAR struct tcb_s *rtcb = this_task();
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if (rtcb && rtcb->task_state == TSTATE_TASK_RUNNING)
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{
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/* Yes.. the task is running normally. Return a reference to the
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* thread-private errno in the TCB of the running task.
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*/
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return &rtcb->pterrno;
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}
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}
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/* We were called either from (1) an interrupt handler or (2) from normally
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* code but in an unhealthy state. In either event, do not permit access to
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* the errno in the TCB of the task at the head of the ready-to-run list.
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* Instead, use a separate errno just for interrupt handlers. Of course, this
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* would have to change if we ever wanted to support nested interrupts or if
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* we really cared about the stability of the errno during those "unhealthy
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* states."
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*/
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return &g_irqerrno;
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}
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