[pve-devel] [PATCH qemu-server v2 1/3] qmeventd: rework 'forced_cleanup' handling and set timeout to 60s

[Dominik Csapak <d.csapak@proxmox.com>]

currently, the 'forced_cleanup' (sending SIGKILL to the qemu process),
is intended to be triggered 5 seconds after sending the initial shutdown
signal (SIGTERM) which is sadly not enough for some setups.

Accidentally, it could be triggered earlier than 5 seconds, if a
SIGALRM triggers in the timespan directly before setting it again.

Also, this approach means that depending on when machines are shutdown
their forced cleanup may happen after 5 seconds, or any time after, if
new vms are shut off in the meantime.

Improve this situation by reworking the way we deal with this cleanup.
We save the time incl. timeout in the CleanupData, and set a timeout
to 'epoll_wait' of 10 seconds, which will then trigger a forced_cleanup.
Remove entries from the forced_cleanup list when that entry is killed,
or when the normal cleanup took place.

To improve the shutdown behaviour, increase the default timeout to 60
seconds, which should be enough, but add a commandline toggle where
users can set it to a different value.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 qmeventd/qmeventd.c | 73 +++++++++++++++++++++++----------------------
 qmeventd/qmeventd.h |  2 ++
 2 files changed, 39 insertions(+), 36 deletions(-)

diff --git a/qmeventd/qmeventd.c b/qmeventd/qmeventd.c
index 8d32827..46bc7eb 100644
--- a/qmeventd/qmeventd.c
+++ b/qmeventd/qmeventd.c
@@ -29,6 +29,7 @@
 #include <signal.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/epoll.h>
 #include <sys/socket.h>
@@ -36,15 +37,19 @@
 #include <sys/un.h>
 #include <sys/wait.h>
 #include <unistd.h>
+#include <time.h>
 
 #include "qmeventd.h"
 
+#define DEFAULT_KILL_TIMEOUT 60
+
 static int verbose = 0;
+static int kill_timeout = DEFAULT_KILL_TIMEOUT;
 static int epoll_fd = 0;
 static const char *progname;
 GHashTable *vm_clients; // key=vmid (freed on remove), value=*Client (free manually)
 GSList *forced_cleanups;
-volatile sig_atomic_t alarm_triggered = 0;
+static int needs_cleanup = 0;
 
 /*
  * Helper functions
@@ -56,6 +61,7 @@ usage()
     fprintf(stderr, "Usage: %s [-f] [-v] PATH\n", progname);
     fprintf(stderr, "  -f       run in foreground (default: false)\n");
     fprintf(stderr, "  -v       verbose (default: false)\n");
+    fprintf(stderr, "  -t <s>   kill timeout (default: %ds)\n", DEFAULT_KILL_TIMEOUT);
     fprintf(stderr, "  PATH     use PATH for socket\n");
 }
 
@@ -469,16 +475,17 @@ terminate_client(struct Client *client)
     int err = kill(client->pid, SIGTERM);
     log_neg(err, "kill");
 
+    time_t timeout = time(NULL) + kill_timeout;
+
     struct CleanupData *data_ptr = malloc(sizeof(struct CleanupData));
     struct CleanupData data = {
 	.pid = client->pid,
-	.pidfd = pidfd
+	.pidfd = pidfd,
+	.timeout = timeout,
     };
     *data_ptr = data;
     forced_cleanups = g_slist_prepend(forced_cleanups, (void *)data_ptr);
-
-    // resets any other alarms, but will fire eventually and cleanup all
-    alarm(5);
+    needs_cleanup = 1;
 }
 
 void
@@ -551,27 +558,16 @@ handle_client(struct Client *client)
     json_tokener_free(tok);
 }
 
-
-/*
- * SIGALRM and cleanup handling
- *
- * terminate_client will set an alarm for 5 seconds and add its client's PID to
- * the forced_cleanups list - when the timer expires, we iterate the list and
- * attempt to issue SIGKILL to all processes which haven't yet stopped.
- */
-
-static void
-alarm_handler(__attribute__((unused)) int signum)
-{
-    alarm_triggered = 1;
-}
-
 static void
-sigkill(void *ptr, __attribute__((unused)) void *unused)
+sigkill(struct CleanupData *ptr, time_t *cur_time)
 {
-    struct CleanupData data = *((struct CleanupData *)ptr);
+    struct CleanupData data = *ptr;
     int err;
 
+    if (data.timeout > *cur_time) {
+	return;
+    }
+
     if (data.pidfd > 0) {
 	err = pidfd_send_signal(data.pidfd, SIGKILL, NULL, 0);
 	(void)close(data.pidfd);
@@ -588,21 +584,23 @@ sigkill(void *ptr, __attribute__((unused)) void *unused)
 	fprintf(stderr, "cleanup failed, terminating pid '%d' with SIGKILL\n",
 		data.pid);
     }
+
+    // remove ourselves from the list
+    forced_cleanups = g_slist_remove(forced_cleanups, ptr);
+    free(ptr);
 }
 
 static void
 handle_forced_cleanup()
 {
-    if (alarm_triggered) {
+    if (g_slist_length(forced_cleanups) > 0) {
 	VERBOSE_PRINT("clearing forced cleanup backlog\n");
-	alarm_triggered = 0;
-	g_slist_foreach(forced_cleanups, sigkill, NULL);
-	g_slist_free_full(forced_cleanups, free);
-	forced_cleanups = NULL;
+	time_t cur_time = time(NULL);
+	g_slist_foreach(forced_cleanups, (GFunc)sigkill, &cur_time);
     }
+    needs_cleanup = g_slist_length(forced_cleanups) > 0;
 }
 
-
 int
 main(int argc, char *argv[])
 {
@@ -611,7 +609,7 @@ main(int argc, char *argv[])
     char *socket_path = NULL;
     progname = argv[0];
 
-    while ((opt = getopt(argc, argv, "hfv")) != -1) {
+    while ((opt = getopt(argc, argv, "hfvt:")) != -1) {
 	switch (opt) {
 	    case 'f':
 		daemonize = 0;
@@ -619,6 +617,15 @@ main(int argc, char *argv[])
 	    case 'v':
 		verbose = 1;
 		break;
+	    case 't':
+		errno = 0;
+		char *endptr = NULL;
+		kill_timeout = strtoul(optarg, &endptr, 10);
+		if (errno != 0 || *endptr != '\0' || kill_timeout == 0) {
+		    usage();
+		    exit(EXIT_FAILURE);
+		}
+		break;
 	    case 'h':
 		usage();
 		exit(EXIT_SUCCESS);
@@ -635,7 +642,6 @@ main(int argc, char *argv[])
     }
 
     signal(SIGCHLD, SIG_IGN);
-    signal(SIGALRM, alarm_handler);
 
     socket_path = argv[optind];
 
@@ -669,11 +675,7 @@ main(int argc, char *argv[])
     int nevents;
 
     for(;;) {
-	nevents = epoll_wait(epoll_fd, events, 1, -1);
-	if (nevents < 0 && errno == EINTR) {
-	    handle_forced_cleanup();
-	    continue;
-	}
+	nevents = epoll_wait(epoll_fd, events, 1, needs_cleanup ? 10*1000 : -1);
 	bail_neg(nevents, "epoll_wait");
 
 	for (int n = 0; n < nevents; n++) {
@@ -688,7 +690,6 @@ main(int argc, char *argv[])
 		handle_client((struct Client *)events[n].data.ptr);
 	    }
 	}
-
 	handle_forced_cleanup();
     }
 }
diff --git a/qmeventd/qmeventd.h b/qmeventd/qmeventd.h
index 2cf1947..1b9cea1 100644
--- a/qmeventd/qmeventd.h
+++ b/qmeventd/qmeventd.h
@@ -7,6 +7,7 @@
 */
 
 #include <sys/syscall.h>
+#include <time.h>
 
 #ifndef __NR_pidfd_open
 #define __NR_pidfd_open 434
@@ -86,6 +87,7 @@ struct Client {
 struct CleanupData {
     pid_t pid;
     int pidfd;
+    time_t timeout;
 };
 
 void handle_qmp_handshake(struct Client *client);
-- 
2.30.2