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poll-loop: Track the poll timeout as an absolute, not a relative time.

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This is a necessary prerequisite for allowing time to be "fast forwarded"
in unit tests, to keep tests that depend on the passage of time from
running in real time.  Without this change, a code sequence like this:

	poll_timer_wait(1000);
	...fast forward time 5 seconds...
	poll_block();

would still sleep for a second, because the poll_loop module would still
have a relative timeout of 1000 ms.

Signed-off-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Ben Pfaff
2011-12-19 14:28:42 -08:00
parent fbac791aea
commit cee03df4f5
3 changed files with 47 additions and 35 deletions
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23
lib/timeval.c
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@@ -268,17 +268,22 @@ time_alarm(unsigned int secs)
}
/* Like poll(), except:
*
* - The timeout is specified as an absolute time, as defined by
* time_msec(), instead of a duration.
*
* - On error, returns a negative error code (instead of setting errno).
*
* - If interrupted by a signal, retries automatically until the original
* 'timeout' expires. (Because of this property, this function will
* timeout is reached. (Because of this property, this function will
* never return -EINTR.)
*
* - As a side effect, refreshes the current time (like time_refresh()).
*/
*
* Stores the number of milliseconds elapsed during poll in '*elapsed'. */
int
time_poll(struct pollfd *pollfds, int n_pollfds, int timeout)
time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
int *elapsed)
{
static long long int last_wakeup;
long long int start;
@@ -292,12 +297,15 @@ time_poll(struct pollfd *pollfds, int n_pollfds, int timeout)
start = time_msec();
blocked = false;
for (;;) {
long long int now = time_msec();
int time_left;
if (timeout > 0) {
long long int elapsed = time_msec() - start;
time_left = timeout >= elapsed ? timeout - elapsed : 0;
if (now >= timeout_when) {
time_left = 0;
} else if ((unsigned long long int) timeout_when - now > INT_MAX) {
time_left = INT_MAX;
} else {
time_left = timeout;
time_left = timeout_when - now;
}
retval = poll(pollfds, n_pollfds, time_left);
@@ -319,6 +327,7 @@ time_poll(struct pollfd *pollfds, int n_pollfds, int timeout)
}
last_wakeup = time_msec();
refresh_rusage();
*elapsed = last_wakeup - start;
return retval;
}