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Prefer POSIX timers if available.

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They avoid a race if the timer is too close to the current time.
* atimer.c (alarm_timer, alarm_timer_ok) [SIGEV_SIGNAL]: New static vars.
(set_alarm) [SIGEV_SIGNAL]: Use POSIX timers if available.
(init_atimer) [SIGEV_SIGAL]: Initialize them.
This commit is contained in:
Paul Eggert 2012-09-25 12:18:05 -07:00
parent eedec3eec8
commit e26fd2e4a9
2 changed files with 39 additions and 6 deletions
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8
src/ChangeLog
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@ -1,3 +1,11 @@
2012-09-25 Paul Eggert <eggert@cs.ucla.edu>
Prefer POSIX timers if available.
They avoid a race if the timer is too close to the current time.
* atimer.c (alarm_timer, alarm_timer_ok) [SIGEV_SIGNAL]: New static vars.
(set_alarm) [SIGEV_SIGNAL]: Use POSIX timers if available.
(init_atimer) [SIGEV_SIGAL]: Initialize them.
2012-09-25 Eli Zaretskii <eliz@gnu.org>
* coding.c (CHAR_STRING_ADVANCE_NO_UNIFY): Make it an alias of

37
src/atimer.c
View file

@ -40,6 +40,13 @@ static struct atimer *stopped_atimers;
static struct atimer *atimers;
/* The alarm timer and whether it was properly initialized, if
POSIX timers are available. */
#ifdef SIGEV_SIGNAL
static timer_t alarm_timer;
static bool alarm_timer_ok;
#endif
/* Block/unblock SIGALRM. */
static void
@ -287,14 +294,25 @@ set_alarm (void)
#ifdef HAVE_SETITIMER
struct itimerval it;
#endif
EMACS_TIME now, interval;
/* Determine s/us till the next timer is ripe. */
EMACS_TIME now = current_emacs_time ();
#ifdef SIGEV_SIGNAL
if (alarm_timer_ok)
{
struct itimerspec ispec;
ispec.it_value = atimers->expiration;
ispec.it_interval.tv_sec = ispec.it_interval.tv_nsec = 0;
if (timer_settime (alarm_timer, 0, &ispec, 0) == 0)
return;
}
#endif
/* Don't set the interval to 0; this disables the timer. */
EMACS_TIME interval = (EMACS_TIME_LE (atimers->expiration, now)
? make_emacs_time (0, 1000 * 1000)
: sub_emacs_time (atimers->expiration, now));
/* Determine interval till the next timer is ripe.
Don't set the interval to 0; this disables the timer. */
now = current_emacs_time ();
interval = (EMACS_TIME_LE (atimers->expiration, now)
? make_emacs_time (0, 1000 * 1000)
: sub_emacs_time (atimers->expiration, now));
#ifdef HAVE_SETITIMER
@ -398,6 +416,13 @@ void
init_atimer (void)
{
struct sigaction action;
#ifdef SIGEV_SIGNAL
struct sigevent sigev;
sigev.sigev_notify = SIGEV_SIGNAL;
sigev.sigev_signo = SIGALRM;
sigev.sigev_value.sival_ptr = &alarm_timer;
alarm_timer_ok = timer_create (CLOCK_REALTIME, &sigev, &alarm_timer) == 0;
#endif
free_atimers = stopped_atimers = atimers = NULL;
/* pending_signals is initialized in init_keyboard.*/
emacs_sigaction_init (&action, handle_alarm_signal);