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From c99c5bb88c8b02f24a2b0b15ea8bc9fe2a8dc6c4 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Pavel=20B=C5=99ezina?= <pbrezina@redhat.com>
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Date: Mon, 22 Aug 2016 13:15:04 +0200
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Subject: [PATCH 116/117] watchdog: cope with time shift
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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When a time is changed into the past during sssd runtime
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(e.g. on boot during time correction), it is possible that
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we never hit watchdog tevent timer since it is based on
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system time.
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This patch adds a past-time shift detection mechanism. If a time
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shift is detected we restart watchdog.
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Resolves:
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https://fedorahosted.org/sssd/ticket/3154
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Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
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Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
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---
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src/util/util_watchdog.c | 41 +++++++++++++++++++++++++++++++++++++++++
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1 file changed, 41 insertions(+)
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diff --git a/src/util/util_watchdog.c b/src/util/util_watchdog.c
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index 5032fddba1b94b3fc7e560162c392dfa57d699cf..1c27d73f13b3042ecb549a2184e1368e8339d199 100644
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--- a/src/util/util_watchdog.c
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+++ b/src/util/util_watchdog.c
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@@ -29,8 +29,39 @@ struct watchdog_ctx {
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struct timeval interval;
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struct tevent_timer *te;
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volatile int ticks;
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+
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+ /* To detect time shift. */
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+ struct tevent_context *ev;
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+ int input_interval;
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+ time_t timestamp;
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} watchdog_ctx;
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+static bool watchdog_detect_timeshift(void)
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+{
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+ time_t prev_time;
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+ time_t cur_time;
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+ errno_t ret;
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+
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+ prev_time = watchdog_ctx.timestamp;
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+ cur_time = watchdog_ctx.timestamp = time(NULL);
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+ if (cur_time < prev_time) {
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+ /* Time shift detected. We need to restart watchdog. */
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+ DEBUG(SSSDBG_IMPORTANT_INFO, "Time shift detected, "
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+ "restarting watchdog!\n");
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+ teardown_watchdog();
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+ ret = setup_watchdog(watchdog_ctx.ev, watchdog_ctx.input_interval);
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+ if (ret != EOK) {
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+ DEBUG(SSSDBG_FATAL_FAILURE, "Unable to restart watchdog "
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+ "[%d]: %s\n", ret, sss_strerror(ret));
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+ orderly_shutdown(1);
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+ }
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+
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+ return true;
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+ }
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+
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+ return false;
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+}
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+
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/* the watchdog is purposefully *not* handled by the tevent
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* signal handler as it is meant to check if the daemon is
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* still processing the event queue itself. A stuck process
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@@ -38,6 +69,12 @@ struct watchdog_ctx {
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* signals either */
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static void watchdog_handler(int sig)
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{
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+ /* Do not count ticks if time shift was detected
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+ * since watchdog was restarted. */
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+ if (watchdog_detect_timeshift()) {
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+ return;
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+ }
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+
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/* if 3 ticks passed by kills itself */
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if (__sync_add_and_fetch(&watchdog_ctx.ticks, 1) > 3) {
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@@ -101,6 +138,10 @@ int setup_watchdog(struct tevent_context *ev, int interval)
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watchdog_ctx.interval.tv_sec = interval;
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watchdog_ctx.interval.tv_usec = 0;
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+ watchdog_ctx.ev = ev;
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+ watchdog_ctx.input_interval = interval;
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+ watchdog_ctx.timestamp = time(NULL);
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+
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/* Start the timer */
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/* we give 1 second head start to the watchdog event */
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its.it_value.tv_sec = interval + 1;
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--
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2.4.11
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