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vfs/poll: round timeout up to next full tick. Calling poll() with timeout less than half tick (thus MSEC2TICK(timeout) => 0) caused returning error with EAGAIN. Instead of rounding timeout down, value should be rounded up. Open Group spec for poll says: "Implementations may place limitations on the granularity of timeout intervals. If the requested timeout interval requires a finer granularity than the implementation supports, the actual timeout interval will be rounded up to the next supported value."

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This commit is contained in:
Jussi Kivilinna 2017-04-28 08:42:37 -06:00 committed by Gregory Nutt
parent 9431fb1d91
commit 37ca797d1c
1 changed files with 20 additions and 1 deletions
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21
fs/vfs/fs_poll.c
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@ -388,6 +388,25 @@ int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
}
else if (timeout > 0)
{
systime_t ticks;
/* "Implementations may place limitations on the granularity of
* timeout intervals. If the requested timeout interval requires
* a finer granularity than the implementation supports, the
* actual timeout interval will be rounded up to the next
* supported value." -- opengroup.org
*
* Round timeout up to next full tick.
*/
#if (MSEC_PER_TICK * USEC_PER_MSEC) != USEC_PER_TICK && \
defined(CONFIG_HAVE_LONG_LONG)
ticks = ((long long)timeout * USEC_PER_MSEC) + (USEC_PER_TICK - 1) /
USEC_PER_TICK;
#else
ticks = (timeout + (MSEC_PER_TICK - 1)) / MSEC_PER_TICK;
#endif
/* Either wait for either a poll event(s), for a signal to occur,
* or for the specified timeout to elapse with no event.
*
@ -396,7 +415,7 @@ int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
* immediately.
*/
ret = sem_tickwait(&sem, clock_systimer(), MSEC2TICK(timeout));
ret = sem_tickwait(&sem, clock_systimer(), ticks);
if (ret < 0)
{
if (ret == -ETIMEDOUT)