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Re-implemented poll() using sem_timedwait()

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This commit is contained in:
Gregory Nutt 2014-09-26 06:28:20 -06:00
parent 365d604463
commit c652092ac4
1 changed files with 37 additions and 57 deletions
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94
fs/fs_poll.c
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@ -46,11 +46,12 @@
#include <assert.h> #include <assert.h>
#include <debug.h> #include <debug.h>
#include <nuttx/wdog.h>
#include <nuttx/sched.h> #include <nuttx/sched.h>
#include <nuttx/clock.h> #include <nuttx/clock.h>
#include <nuttx/fs/fs.h> #include <nuttx/fs/fs.h>
#include <arch/irq.h>
#include "fs_internal.h" #include "fs_internal.h"
#ifndef CONFIG_DISABLE_POLL #ifndef CONFIG_DISABLE_POLL
@ -191,39 +192,6 @@ static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds, sem_t *sem)
} }
#endif #endif
/****************************************************************************
* Name: poll_peek
*
* Description:
* Peek into each file descriptor whether poll events are already available.
*
* Return values:
* TRUE : Poll events available.
* FALSE: No poll events available.
*
****************************************************************************/
#if CONFIG_NFILE_DESCRIPTORS > 0
static inline int poll_peek(FAR struct pollfd *fds, nfds_t nfds)
{
int i = 0;
/* Process each descriptor in the list */
for (i = 0; i < nfds; i++)
{
/* Peek if any events are currently posted */
if (fds[i].revents != 0)
{
return TRUE;
}
}
return FALSE;
}
#endif
/**************************************************************************** /****************************************************************************
* Name: poll_teardown * Name: poll_teardown
* *
@ -327,7 +295,8 @@ static void poll_timeout(int argc, uint32_t isem, ...)
int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout) int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
{ {
WDOG_ID wdog; struct timespec abstime;
irqstate_t flags;
sem_t sem; sem_t sem;
int count = 0; int count = 0;
int ret; int ret;
@ -338,36 +307,47 @@ int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
{ {
if (timeout == 0) if (timeout == 0)
{ {
/* Poll returns immediately whether we have a poll event or not. /* Poll returns immediately whether we have a poll event or not. */
*
* ATTENTION: This branch is explicitly necessary to avoid the ret = sem_trywait(&sem);
* blocking behavior of the watchdog implementation which results
* in an event jittering until the current time-slice has been
* finished because watchdog events are only evaluated during the
* execution of the Timer-ISR (SysTick/Time-Slice = 10ms -->
* Jitter up to 10ms).
*/
} }
else if (timeout > 0) else if (timeout > 0)
{ {
/* Either wait for poll event(s) with specified timeout if no time_t sec;
* events are currently available or return immediately. Note uint32-_t nsec;
* that the millisecond timeout has to be converted to system
* clock ticks for wd_start /* Either wait for either a poll event(s) to occur or for the
* specified timeout to elapse with no event.
*
* NOTE: If a poll event is pending (i.e., the semaphore has already
* been incremented), sem_timedwait() will not wait, but will return
* immediately.
*/ */
if (poll_peek(fds, nfds) == FALSE) sec = timeout / MSEC_PER_SEC;
{ nsec = (timout - MSEC_PER_SEC * sec) * NSEC_PER_MSEC;
wdog = wd_create();
wd_start(wdog, MSEC2TICK(timeout), poll_timeout, 1, /* Make sure that the following are atomic by disabling interrupts.
(uint32_t)&sem); * Interrupts will be re-enabled while we are waiting.
poll_semtake(&sem); */
wd_delete(wdog);
} flags = irqsave();
(void)clock_gettime(CLOCK_REALTIME, &abstime);
abstime.tv_sec += sec;
abstime.tv_nsec += nsec;
if (abstime.tv_nsec > NSEC_PER_SEC)
{
abstime.tv_sec++;
abstime.tv_nsec -= NSEC_PER_SEC;
}
ret = sem_timedwai&sem, &abstime);
irqrestore(flags);
} }
else else
{ {
/* Wait for the poll event with no timeout (blocking indefinitely) */ /* Wait for the poll event with no timeout */
poll_semtake(&sem); poll_semtake(&sem);
} }