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kqueue: don't arbitrarily restrict long-past values for NOTE_ABSTIME
NOTE_ABSTIME values are converted to values relative to boottime in filt_timervalidate(), and negative values are currently rejected. We don't reject times in the past in general, so clamp this up to 0 as needed such that the timer fires immediately rather than imposing what looks like an arbitrary restriction. Another possible scenario is that the system clock had to be adjusted by ~minutes or ~hours and we have less than that in terms of uptime, making a reasonable short-timeout suddenly invalid. Firing it is still a valid choice in this scenario so that applications can at least expect a consistent behavior. Reviewed by: kib, markj Discussed with: allanjude Differential Revision: https://reviews.freebsd.org/D32230
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@ -798,13 +798,13 @@ filt_timervalidate(struct knote *kn, sbintime_t *to)
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return (EINVAL);
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*to = timer2sbintime(kn->kn_sdata, kn->kn_sfflags);
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if (*to < 0)
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return (EINVAL);
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if ((kn->kn_sfflags & NOTE_ABSTIME) != 0) {
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getboottimebin(&bt);
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sbt = bttosbt(bt);
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*to -= sbt;
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*to = MAX(0, *to - sbt);
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}
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if (*to < 0)
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return (EINVAL);
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return (0);
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}
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@ -815,9 +815,14 @@ filt_timerattach(struct knote *kn)
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sbintime_t to;
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int error;
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to = -1;
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error = filt_timervalidate(kn, &to);
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if (error != 0)
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return (error);
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KASSERT((kn->kn_flags & EV_ONESHOT) != 0 || to > 0,
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("%s: periodic timer has a calculated zero timeout", __func__));
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KASSERT(to >= 0,
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("%s: timer has a calculated negative timeout", __func__));
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if (atomic_fetchadd_int(&kq_ncallouts, 1) + 1 > kq_calloutmax) {
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atomic_subtract_int(&kq_ncallouts, 1);
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@ -247,6 +247,88 @@ test_abstime(void)
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success();
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}
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static void
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test_abstime_preboot(void)
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{
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const char *test_id = "kevent(EVFILT_TIMER (PREBOOT), EV_ONESHOT, NOTE_ABSTIME)";
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struct kevent kev;
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struct timespec btp;
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uint64_t end, start, stop;
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test_begin(test_id);
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test_no_kevents();
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/*
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* We'll expire it at just before system boot (roughly) with the hope that
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* we'll get an ~immediate expiration, just as we do for any value specified
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* between system boot and now.
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*/
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start = now();
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if (clock_gettime(CLOCK_BOOTTIME, &btp) != 0)
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err(1, "%s", test_id);
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end = start - SEC_TO_US(btp.tv_sec + 1);
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EV_SET(&kev, vnode_fd, EVFILT_TIMER, EV_ADD | EV_ONESHOT,
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NOTE_ABSTIME | NOTE_USECONDS, end, NULL);
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if (kevent(kqfd, &kev, 1, NULL, 0, NULL) < 0)
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err(1, "%s", test_id);
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/* Retrieve the event */
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kev.flags = EV_ADD | EV_ONESHOT;
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kev.data = 1;
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kev.fflags = 0;
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kevent_cmp(&kev, kevent_get(kqfd));
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stop = now();
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if (stop < end)
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err(1, "too early %jd %jd", (intmax_t)stop, (intmax_t)end);
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/* Check if the event occurs again */
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sleep(3);
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test_no_kevents();
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success();
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}
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static void
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test_abstime_postboot(void)
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{
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const char *test_id = "kevent(EVFILT_TIMER (POSTBOOT), EV_ONESHOT, NOTE_ABSTIME)";
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struct kevent kev;
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uint64_t end, start, stop;
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const int timeout_sec = 1;
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test_begin(test_id);
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test_no_kevents();
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/*
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* Set a timer for 1 second ago, it should fire immediately rather than
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* being rejected.
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*/
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start = now();
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end = start - SEC_TO_US(timeout_sec);
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EV_SET(&kev, vnode_fd, EVFILT_TIMER, EV_ADD | EV_ONESHOT,
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NOTE_ABSTIME | NOTE_USECONDS, end, NULL);
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if (kevent(kqfd, &kev, 1, NULL, 0, NULL) < 0)
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err(1, "%s", test_id);
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/* Retrieve the event */
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kev.flags = EV_ADD | EV_ONESHOT;
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kev.data = 1;
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kev.fflags = 0;
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kevent_cmp(&kev, kevent_get(kqfd));
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stop = now();
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if (stop < end)
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err(1, "too early %jd %jd", (intmax_t)stop, (intmax_t)end);
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/* Check if the event occurs again */
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sleep(3);
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test_no_kevents();
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success();
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}
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static void
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test_update(void)
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{
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@ -517,6 +599,8 @@ test_evfilt_timer(void)
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test_oneshot();
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test_periodic();
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test_abstime();
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test_abstime_preboot();
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test_abstime_postboot();
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test_update();
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test_update_equal();
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test_update_expired();
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