Re: [PATCH 23/26] rpc: fix shutdown sequence when preserving state

The preserving of state (ie running VMs) requires a fully functional daemon and hypervisor driver. If any part has started shutting down then saving state may fail, or worse, hang. The current shutdown sequence does not guarantee safe ordering, as we synchronize with the state saving thread only after the hypervisor driver has had its 'shutdownPrepare' callback invoked. In the case of QEMU this means that worker threads processing monitor events may well have been stopped. This implements a full state machine that has a well defined ordering that an earlier commit documented as the desired semantics. With this change, nothing will start shutting down if the state saving thread is still running. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- src/remote/remote_daemon.c | 4 +- src/rpc/virnetdaemon.c | 103 ++++++++++++++++++++++++++----------- 2 files changed, 76 insertions(+), 31 deletions(-) diff --git a/src/remote/remote_daemon.c b/src/remote/remote_daemon.c index e03ee1de5a..f64ecad7f5 100644 --- a/src/remote/remote_daemon.c +++ b/src/remote/remote_daemon.c @@ -617,8 +617,8 @@ static void daemonRunStateInit(void *opaque) NULL, G_DBUS_SIGNAL_FLAGS_NONE, handleSystemMessageFunc, - dmn, - NULL); + dmn, + NULL); /* Only now accept clients from network */ virNetDaemonUpdateServices(dmn, true);

diff --git a/src/rpc/virnetdaemon.c b/src/rpc/virnetdaemon.c index 7f14c5420a..d1d7bae569 100644 --- a/src/rpc/virnetdaemon.c +++ b/src/rpc/virnetdaemon.c @@ -39,6 +39,15 @@ VIR_LOG_INIT("rpc.netdaemon"); +typedef enum { + VIR_NET_DAEMON_QUIT_NONE, + VIR_NET_DAEMON_QUIT_REQUESTED, + VIR_NET_DAEMON_QUIT_PRESERVING, + VIR_NET_DAEMON_QUIT_READY, + VIR_NET_DAEMON_QUIT_WAITING, + VIR_NET_DAEMON_QUIT_COMPLETED, +} virNetDaemonQuitPhase;

@@ -753,7 +762,7 @@ virNetDaemonRun(virNetDaemon *dmn) virSystemdNotifyReady(); VIR_DEBUG("dmn=%p quit=%d", dmn, dmn->quit); - while (!dmn->finished) { + while (dmn->quit != VIR_NET_DAEMON_QUIT_COMPLETED) { virNetDaemonShutdownTimerUpdate(dmn); virObjectUnlock(dmn); @@ -767,17 +776,30 @@ virNetDaemonRun(virNetDaemon *dmn) virHashForEach(dmn->servers, daemonServerProcessClients, NULL); /* don't shutdown services when performing an exec-restart */ - if (dmn->quit && dmn->execRestart) + if (dmn->quit == VIR_NET_DAEMON_QUIT_REQUESTED && dmn->execRestart) goto cleanup; - if (dmn->quit && dmn->finishTimer == -1) { + if (dmn->quit == VIR_NET_DAEMON_QUIT_REQUESTED) { + VIR_DEBUG("Process quit request"); virHashForEach(dmn->servers, daemonServerClose, NULL); + + if (dmn->shutdownPreserveThread) { + VIR_DEBUG("Shutdown preserve thread running"); + dmn->quit = VIR_NET_DAEMON_QUIT_PRESERVING; + } else { + VIR_DEBUG("Ready to shutdown"); + dmn->quit = VIR_NET_DAEMON_QUIT_READY; + } + } + + if (dmn->quit == VIR_NET_DAEMON_QUIT_READY) { + VIR_DEBUG("Starting shutdown, running prepare"); if (dmn->shutdownPrepareCb && dmn->shutdownPrepareCb() < 0) break; - if ((dmn->finishTimer = virEventAddTimeout(30 * 1000, - virNetDaemonFinishTimer, - dmn, NULL)) < 0) { + if ((dmn->quitTimer = virEventAddTimeout(30 * 1000, + virNetDaemonQuitTimer, + dmn, NULL)) < 0) { VIR_WARN("Failed to register finish timer."); break; } @@ -787,6 +809,9 @@ virNetDaemonRun(virNetDaemon *dmn) VIR_WARN("Failed to register join thread."); break; } + + VIR_DEBUG("Waiting for shutdown completion"); + dmn->quit = VIR_NET_DAEMON_QUIT_WAITING;

@@ -808,7 +833,7 @@ virNetDaemonQuit(virNetDaemon *dmn) VIR_LOCK_GUARD lock = virObjectLockGuard(dmn); VIR_DEBUG("Quit requested %p", dmn); - dmn->quit = true; + dmn->quit = VIR_NET_DAEMON_QUIT_REQUESTED; } @@ -818,7 +843,7 @@ virNetDaemonQuitExecRestart(virNetDaemon *dmn) VIR_LOCK_GUARD lock = virObjectLockGuard(dmn); VIR_DEBUG("Exec-restart requested %p", dmn); - dmn->quit = true; + dmn->quit = VIR_NET_DAEMON_QUIT_REQUESTED; dmn->execRestart = true; }

@@ -827,12 +852,21 @@ static void virNetDaemonPreserveWorker(void *opaque) { virNetDaemon *dmn = opaque; - VIR_DEBUG("Begin stop dmn=%p", dmn); + VIR_DEBUG("Begin preserve dmn=%p", dmn); dmn->shutdownPreserveCb(); - VIR_DEBUG("Completed stop dmn=%p", dmn); + VIR_DEBUG("Completed preserve dmn=%p", dmn); + VIR_WITH_OBJECT_LOCK_GUARD(dmn) { + if (dmn->quit == VIR_NET_DAEMON_QUIT_PRESERVING) { + VIR_DEBUG("Marking shutdown as ready"); + dmn->quit = VIR_NET_DAEMON_QUIT_READY; + } + g_clear_pointer(&dmn->shutdownPreserveThread, g_free); + } + + VIR_DEBUG("End preserve dmn=%p", dmn); virObjectUnref(dmn); } @@ -840,15 +874,26 @@ static void virNetDaemonPreserveWorker(void *opaque) void virNetDaemonPreserve(virNetDaemon *dmn) { VIR_LOCK_GUARD lock = virObjectLockGuard(dmn); + VIR_DEBUG("Preserve state request"); - if (!dmn->shutdownPreserveCb || - dmn->shutdownPreserveThread) + if (!dmn->shutdownPreserveCb) { + VIR_DEBUG("No preserve callback registered"); return; + } + if (dmn->shutdownPreserveThread) { + VIR_DEBUG("Preserve state thread already running"); + return; + } + + if (dmn->quit != VIR_NET_DAEMON_QUIT_NONE) { + VIR_WARN("Already initiated shutdown sequence, unable to preserve state"); + return; + } virObjectRef(dmn); dmn->shutdownPreserveThread = g_new0(virThread, 1); - if (virThreadCreateFull(dmn->shutdownPreserveThread, true, + if (virThreadCreateFull(dmn->shutdownPreserveThread, false,

virNetDaemonPreserveWorker, "daemon-stop", false, dmn) < 0) { virObjectUnref(dmn);