shutdown: already sync IO before we enter the final killing spree

This way, slow IO journald has to wait for can't cause it to reach the killing
spree timeout and is hit by SIGKILL in addition to SIGTERM.

diff --git a/src/core/shutdown.c b/src/core/shutdown.c
index e14755d..a795d87 100644 (file)
--- a/src/core/shutdown.c
+++ b/src/core/shutdown.c
@@ -157,7 +157,6 @@ static int switch_root_initramfs(void) {
         return switch_root("/run/initramfs", "/oldroot", false, MS_BIND);
 }
 
-
 int main(int argc, char *argv[]) {
         bool need_umount, need_swapoff, need_loop_detach, need_dm_detach;
         bool in_container, use_watchdog = false;
@@ -203,20 +202,25 @@ int main(int argc, char *argv[]) {
         }
 
         (void) cg_get_root_path(&cgroup);
+        in_container = detect_container() > 0;
 
         use_watchdog = !!getenv("WATCHDOG_USEC");
 
-        /* lock us into memory */
+        /* Lock us into memory */
         mlockall(MCL_CURRENT|MCL_FUTURE);
 
+        /* Synchronize everything that is not written to disk yet at this point already. This is a good idea so that
+         * slow IO is processed here already and the final process killing spree is not impacted by processes
+         * desperately trying to sync IO to disk within their timeout. */
+        if (!in_container)
+                sync();
+
         log_info("Sending SIGTERM to remaining processes...");
         broadcast_signal(SIGTERM, true, true);
 
         log_info("Sending SIGKILL to remaining processes...");
         broadcast_signal(SIGKILL, true, false);
 
-        in_container = detect_container() > 0;
-
         need_umount = !in_container;
         need_swapoff = !in_container;
         need_loop_detach = !in_container;
@@ -345,10 +349,10 @@ int main(int argc, char *argv[]) {
                           need_loop_detach ? " loop devices," : "",
                           need_dm_detach ? " DM devices," : "");
 
-        /* The kernel will automaticall flush ATA disks and suchlike
-         * on reboot(), but the file systems need to be synce'd
-         * explicitly in advance. So let's do this here, but not
-         * needlessly slow down containers. */
+        /* The kernel will automatically flush ATA disks and suchlike on reboot(), but the file systems need to be
+         * sync'ed explicitly in advance. So let's do this here, but not needlessly slow down containers. Note that we
+         * sync'ed things already once above, but we did some more work since then which might have caused IO, hence
+         * let's doit once more. */
         if (!in_container)
                 sync();