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nuttx/sched/pthread_condtimedwait.c
patacongo 20970888b7 Keep interrupts disabled until we sample errno 
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@97 42af7a65-404d-4744-a932-0658087f49c3
2007-03-19 16:39:14 +00:00

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/************************************************************
* pthread_condtimedwait.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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/compiler.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>
#include <time.h>
#include <errno.h>
#include <wdog.h>
#include <debug.h>
#include "os_internal.h"
#include "pthread_internal.h"
#include "clock_internal.h"
/************************************************************
* Definitions
************************************************************/
#define ECHO_COND_WAIT_SIGNO 3
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Global Variables
************************************************************/
/************************************************************
* Private Variables
************************************************************/
/************************************************************
* Private Functions
************************************************************/
/************************************************************
* Function: pthread_condtimedout
*
* Description:
* This function is called if the timeout elapses before
* the condition is signaled.
*
* Parameters:
* argc - the number of arguments (should be 2)
* pid - the task ID of the task to wateup
* signo - The signal to use to wake up the task
*
* Return Value:
* None
*
* Assumptions:
*
************************************************************/
static void pthread_condtimedout(int argc, uint32 pid, uint32 signo, ...)
{
#ifdef CONFIG_CAN_PASS_STRUCTS
union sigval value;
/* Send the specified signal to the specified task. */
value.sival_ptr = NULL;
(void)sigqueue((int)pid, (int)signo, value);
#else
(void)sigqueue((int)pid, (int)signo, NULL);
#endif
}
/************************************************************
* Function: pthread_timeoutticks
*
* Description:
* Convert a timespec delay to system timer ticks.
*
* Parameters:
* abstime - wait until this absolute time
*
* Return Value:
* The relative number of ticks to wait (or ERROR on
* failure;
*
* Assumptions:
* Interrupts should be disabled so that the time is
* not changing during the calculation
*
************************************************************/
int pthread_timeouticks(const struct timespec *abstime, int *ticks)
{
struct timespec currtime;
struct timespec reltime;
sint32 relusec;
int ret;
/* Convert the timespec to clock ticks. NOTE: Here we use
* internal knowledge that CLOCK_REALTIME is defined to be zero!
*/
ret = clock_gettime(0, &currtime);
if (ret)
{
return EINVAL;
}
/* The relative time to wait is the absolute time minus the
* current time.
*/
reltime.tv_nsec = (abstime->tv_nsec - currtime.tv_nsec);
reltime.tv_sec = (abstime->tv_sec - currtime.tv_sec);
/* Check if we were supposed to borrow from the seconds to
* borrow from the seconds
*/
if (reltime.tv_nsec < 0)
{
reltime.tv_nsec += NSEC_PER_SEC;
reltime.tv_sec -= 1;
}
/* Convert this relative time into microseconds.*/
relusec = reltime.tv_sec * USEC_PER_SEC +
reltime.tv_nsec / NSEC_PER_USEC;
/* Convert microseconds to clock ticks */
*ticks = relusec / USEC_PER_TICK;
return OK;
}
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* Function: pthread_cond_timedwait
*
* Description:
* A thread can perform a timed wait on a condition variable.
*
* Parameters:
* cond - the condition variable to wait on
* mutex - the mutex that protects the condition variable
* abstime - wait until this absolute time
*
* Return Value:
* OK (0) on success; ERROR (-1) on failure with errno
* set appropriately.
*
* Assumptions:
* Timing is of resolution 1 msec, with +/-1 millisecond
* accuracy.
*
************************************************************/
int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
const struct timespec *abstime)
{
WDOG_ID wdog;
sint32 ticks;
int mypid = (int)getpid();
irqstate_t int_state;
int ret = OK;
int status;
dbg("cond=0x%p mutex=0x%p abstime=0x%p\n", cond, mutex, abstime);
/* Make sure that non-NULL references were provided. */
if (!cond || !mutex)
{
ret = EINVAL;
}
/* Make sure that the caller holds the mutex */
else if (mutex->pid != mypid)
{
ret = EPERM;
}
/* If no wait time is provided, this function degenerates to
* the same behavior as pthread_cond_wait().
*/
else if (!abstime)
{
ret = pthread_cond_wait(cond, mutex);
}
else
{
/* Create a watchdog */
wdog = wd_create();
if (!wdog)
{
ret = EINVAL;
}
else
{
dbg("Give up mutex...\n");
/* We must disable pre-emption and interrupts here so that
* the time stays valid until the wait begins. This adds
* complexity because we assure that interrupts and
* pre-emption are re-enabled correctly.
*/
sched_lock();
int_state = irqsave();
/* Convert the timespec to clock ticks. We must disable pre-emption
* here so that this time stays valid until the wait begins.
*/
ret = pthread_timeouticks(abstime, &ticks);
if (ret)
{
/* Restore interrupts (pre-emption will be enabled when
* we fall through the if/then/else
*/
irqrestore(int_state);
}
else
{
/* Check the absolute time to wait. If it is now or in the past, then
* just return with the timedout condition.
*/
if (ticks <= 0)
{
/* Restore interrupts and indicate that we have already timed out.
* (pre-emption will be enabled when we fall through the
* if/then/else
*/
irqrestore(int_state);
ret = ETIMEDOUT;
}
else
{
/* Give up the mutex */
mutex->pid = 0;
ret = pthread_givesemaphore((sem_t*)&mutex->sem);
if (ret)
{
/* Restore interrupts (pre-emption will be enabled when
* we fall through the if/then/else)
*/
irqrestore(int_state);
}
else
{
/* Start the watchdog */
wd_start(wdog, ticks, (wdentry_t)pthread_condtimedout,
2, (uint32)mypid, (uint32)ECHO_COND_WAIT_SIGNO);
/* Take the condition semaphore. Do not restore interrupts
* until we return from the wait. This is necessary to
* make sure that the watchdog timer and the condition wait
* are started atomically.
*/
status = sem_wait((sem_t*)&cond->sem);
/* Did we get the condition semaphore. */
if (status != OK)
{
/* NO.. Handle the special case where the semaphore wait was
* awakened by the receipt of a signal -- presumably the
* signal posted by pthread_condtimedout().
*/
if (*get_errno_ptr() == EINTR)
{
dbg("Timedout!\n");
ret = ETIMEDOUT;
}
else
{
ret = EINVAL;
}
}
/* The interrupts stay disabled until after we sample the errno.
* This is because when debug is enabled and the console is used
* for debug output, then the errno can be altered by interrupt
* handling! (bad)
*/
irqrestore(int_state);
}
/* Reacquire the mutex (retaining the ret). */
dbg("Re-locking...\n");
status = pthread_takesemaphore((sem_t*)&mutex->sem);
if (!status)
{
mutex->pid = mypid;
}
else if (!ret)
{
ret = status;
}
}
/* Re-enable pre-emption (It is expected that interrupts
* have already been re-enabled in the above logic)
*/
sched_unlock();
}
/* We no longer need the watchdog */
wd_delete(wdog);
}
}
dbg("Returning %d\n", ret);
return ret;
}
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