1 files changed, 193 insertions, 0 deletions
diff --git a/src/wdt.c b/src/wdt.c
new file mode 100644
index 0000000..865bb7b
--- /dev/null
+++ b/src/wdt.c
@@ -0,0 +1,193 @@
+/*
+ * Thread lockup detection
+ *
+ * Copyright 2000-2019 Willy Tarreau <willy@haproxy.org>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <signal.h>
+#include <time.h>
+
+#include <haproxy/api.h>
+#include <haproxy/clock.h>
+#include <haproxy/debug.h>
+#include <haproxy/errors.h>
+#include <haproxy/global.h>
+#include <haproxy/signal-t.h>
+#include <haproxy/thread.h>
+#include <haproxy/tools.h>
+
+
+/*
+ * It relies on timer_create() and timer_settime() which are only available in
+ * this case.
+ */
+#if defined(USE_RT) && defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0) && defined(_POSIX_THREAD_CPUTIME)
+
+/* define a dummy value to designate "no timer". Use only 32 bits. */
+#ifndef TIMER_INVALID
+#define TIMER_INVALID ((timer_t)(unsigned long)(0xfffffffful))
+#endif
+
+static timer_t per_thread_wd_timer[MAX_THREADS];
+
+/* Setup (or ping) the watchdog timer for thread <thr>. Returns non-zero on
+ * success, zero on failure. It interrupts once per second of CPU time. It
+ * happens that timers based on the CPU time are not automatically re-armed
+ * so we only use the value and leave the interval unset.
+ */
+int wdt_ping(int thr)
+{
+	struct itimerspec its;
+
+	its.it_value.tv_sec    = 1; its.it_value.tv_nsec    = 0;
+	its.it_interval.tv_sec = 0; its.it_interval.tv_nsec = 0;
+	return timer_settime(per_thread_wd_timer[thr], 0, &its, NULL) == 0;
+}
+
+/* This is the WDTSIG signal handler */
+void wdt_handler(int sig, siginfo_t *si, void *arg)
+{
+	unsigned long long n, p;
+	ulong thr_bit;
+	int thr, tgrp;
+
+	switch (si->si_code) {
+	case SI_TIMER:
+		/* A thread's timer fired, the thread ID is in si_int. We have
+		 * no guarantee that the thread handling this signal is in any
+		 * way related to the one triggering it, so we need to retrieve
+		 * the thread number from there. Note: this thread might
+		 * continue to execute in parallel.
+		 */
+		thr = si->si_value.sival_int;
+
+		/* cannot happen unless an unknown timer tries to play with our
+		 * nerves. Let's die for now if this happens.
+		 */
+		if (thr < 0 || thr >= global.nbthread)
+			break;
+
+		tgrp = ha_thread_info[thr].tgid;
+		thr_bit = ha_thread_info[thr].ltid_bit;
+		p = ha_thread_ctx[thr].prev_cpu_time;
+		n = now_cpu_time_thread(thr);
+
+		/* not yet reached the deadline of 1 sec,
+		 * or p wasn't initialized yet
+		 */
+		if (!p || n - p < 1000000000UL)
+			goto update_and_leave;
+
+		if ((_HA_ATOMIC_LOAD(&ha_thread_ctx[thr].flags) & TH_FL_SLEEPING) ||
+		    (_HA_ATOMIC_LOAD(&ha_tgroup_ctx[tgrp-1].threads_harmless) & thr_bit)) {
+			/* This thread is currently doing exactly nothing
+			 * waiting in the poll loop (unlikely but possible),
+			 * waiting for all other threads to join the rendez-vous
+			 * point (common), or waiting for another thread to
+			 * finish an isolated operation (unlikely but possible).
+			 */
+			goto update_and_leave;
+		}
+
+		/* So the thread indeed appears locked up. In order to be
+		 * certain that we're not witnessing an exceptional spike of
+		 * CPU usage due to a configuration issue (like running tens
+		 * of thousands of tasks in a single loop), we'll check if the
+		 * scheduler is still alive by setting the TH_FL_STUCK flag
+		 * that the scheduler clears when switching to the next task.
+		 * If it's already set, then it's our second call with no
+		 * progress and the thread is dead.
+		 */
+		if (!(_HA_ATOMIC_LOAD(&ha_thread_ctx[thr].flags) & TH_FL_STUCK)) {
+			_HA_ATOMIC_OR(&ha_thread_ctx[thr].flags, TH_FL_STUCK);
+			goto update_and_leave;
+		}
+
+		/* No doubt now, there's no hop to recover, die loudly! */
+		break;
+
+#if defined(USE_THREAD) && defined(SI_TKILL) /* Linux uses this */
+
+	case SI_TKILL:
+		/* we got a pthread_kill, stop on it */
+		thr = tid;
+		break;
+
+#elif defined(USE_THREAD) && defined(SI_LWP) /* FreeBSD uses this */
+
+	case SI_LWP:
+		/* we got a pthread_kill, stop on it */
+		thr = tid;
+		break;
+
+#endif
+	default:
+		/* unhandled other conditions */
+		return;
+	}
+
+	/* By default we terminate. If we're not on the victim thread, better
+	 * bounce the signal there so that we produce a cleaner stack trace
+	 * with the other thread interrupted exactly where it was running and
+	 * the current one not involved in this.
+	 */
+#ifdef USE_THREAD
+	if (thr != tid)
+		ha_tkill(thr, sig);
+	else
+#endif
+		ha_panic();
+	return;
+
+ update_and_leave:
+	wdt_ping(thr);
+}
+
+int init_wdt_per_thread()
+{
+	if (!clock_setup_signal_timer(&per_thread_wd_timer[tid], WDTSIG, tid))
+		goto fail1;
+
+	if (!wdt_ping(tid))
+		goto fail2;
+
+	return 1;
+
+ fail2:
+	timer_delete(per_thread_wd_timer[tid]);
+ fail1:
+	per_thread_wd_timer[tid] = TIMER_INVALID;
+	ha_warning("Failed to setup watchdog timer for thread %u, disabling lockup detection.\n", tid);
+	return 1;
+}
+
+void deinit_wdt_per_thread()
+{
+	if (per_thread_wd_timer[tid] != TIMER_INVALID)
+		timer_delete(per_thread_wd_timer[tid]);
+}
+
+/* registers the watchdog signal handler and returns 0. This sets up the signal
+ * handler for WDTSIG, so it must be called once per process.
+ */
+int init_wdt()
+{
+	struct sigaction sa;
+
+	sa.sa_handler = NULL;
+	sa.sa_sigaction = wdt_handler;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_SIGINFO;
+	sigaction(WDTSIG, &sa, NULL);
+	return ERR_NONE;
+}
+
+REGISTER_POST_CHECK(init_wdt);
+REGISTER_PER_THREAD_INIT(init_wdt_per_thread);
+REGISTER_PER_THREAD_DEINIT(deinit_wdt_per_thread);
+#endif