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/****************************************************************************
* sched/errno/errno_getptr.c
*
* Copyright (C) 2007, 2008, 2011, 2014 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 "sched/sched.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#undef get_errno_ptr
#undef errno
/****************************************************************************
* Private Data
****************************************************************************/
/* This is a 'dummy' errno value to use in context where there is no valid
* errno location to use. For example, when running from an interrupt handler
* or early in initialization when task structures have not yet been
* initialized.
*/
static int g_irqerrno;
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: get_errno_ptr
*
* Description:
* Return a pointer to the thread specific errno.
*
* Parameters:
* None
*
* Return Value:
* A pointer to the per-thread errno variable.
*
* Assumptions:
*
****************************************************************************/
FAR int *get_errno_ptr(void)
{
/* Check if this function was called from an interrupt handler. In that
* case, we have to do things a little differently to prevent the interrupt
* handler from modifying the tasks errno value.
*/
if (!up_interrupt_context())
{
/* We were called from the normal tasking context. Verify that the
* task at the head of the ready-to-run list is actually running. It
* may not be running during very brief times during context switching
* logic (see, for example, task_exit.c).
*
* There is also a corner case early in the initialization sequence:
* The ready to run list may not yet be initialized and g_readytorun.head
* may be NULL.
*/
FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
if (rtcb && rtcb->task_state == TSTATE_TASK_RUNNING)
{
/* Yes.. the task is running normally. Return a reference to the
* thread-private errno in the TCB of the running task.
*/
return &rtcb->pterrno;
}
}
/* We were called either from (1) an interrupt handler or (2) from normally
* code but in an unhealthy state. In either event, do not permit access to
* the errno in the TCB of the task at the head of the ready-to-run list.
* Instead, use a separate errno just for interrupt handlers. Of course, this
* would have to change if we ever wanted to support nested interrupts or if
* we really cared about the stability of the errno during those "unhealthy
* states."
*/
return &g_irqerrno;
}
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