When the libvirt daemon is restarted it tries to reconnect to running qemu domains. Since commit d38897a5d4b1880e1998394b2a37bba979bbdff1 the re-connection code runs in separate threads. In the original implementation the maximum of domain ID's (that is used as an initializer for numbering guests created next) while libvirt was reconnecting to the guest. With the threaded implementation this opens a possibility for race conditions with the thread that is autostarting guests. When there's a guest running with id 1 and the daemon is restarted. The autostart code is reached first and spawns the first guest that should be autostarted as id 1. This results into the following unwanted situation: # virsh list Id Name State ---------------------------------------------------- 1 guest1 running 1 guest2 running This patch extracts the detection code before the re-connection threads are started so that the maximum id of the guests being reconnected to is known. The only semantic change created by this is if the guest with greatest ID quits before we are able to reconnect it's ID is used anyway as the greatest one as without this patch the greatest ID of a process we could successfuly reconnect to would be used. --- src/qemu/qemu_driver.c | 21 +++++++++++++++++++++ src/qemu/qemu_process.c | 3 --- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 3309f34..8ca8913 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -590,6 +590,20 @@ qemuDomainNetsRestart(void *payload, virDomainObjUnlock(vm); } + +static void +qemuDomainFindMaxID(void *payload, + const void *name ATTRIBUTE_UNUSED, + void *data) +{ + virDomainObjPtr vm = payload; + int *driver_maxid = data; + + if (vm->def->id >= *driver_maxid) + *driver_maxid = vm->def->id + 1; +} + + /** * qemudStartup: * @@ -863,6 +877,13 @@ qemudStartup(int privileged) { NULL, NULL) < 0) goto error; + /* find the maximum ID from active and transient configs to initialize + * the driver with. This is to avoid race between autostart and reconnect + * threads */ + virHashForEach(qemu_driver->domains.objs, + qemuDomainFindMaxID, + &(qemu_driver->nextvmid)); + virHashForEach(qemu_driver->domains.objs, qemuDomainNetsRestart, NULL); conn = virConnectOpen(qemu_driver->uri); diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index d8cf4c3..8bf80e7 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -3230,9 +3230,6 @@ qemuProcessReconnect(void *opaque) goto error; } - if (obj->def->id >= driver->nextvmid) - driver->nextvmid = obj->def->id + 1; - endjob: if (!qemuDomainObjEndJob(driver, obj)) obj = NULL; -- 1.8.0