When stop libvirtd is used, libvirtd exits the eventloop and cleans up     the driverState first. Then release threadPool. If the workers thread     is still executing at this time, it needs to access driverState.     If the value in driverState is not judged at this time, direct access     will cause an abnormal exit and damage the cache file of libvirt.     In our example, the migration task is in progress at this time,     the source is waiting for the target libvirtd dstFinish to return,     the source libvirtd is stopped, and a crash occurs. After start libvirtd,     the corresponding virtual machine process cannot be managed by libvirt     stack:     #0  virSecurityManagerGetNested (mgr=0x7f76141143c0) at security/security_manager.c:1033     1033     if (STREQ("stack", mgr->drv->name))     (gdb) bt     #0  virSecurityManagerGetNested (mgr=0x7f76141143c0) at security/security_manager.c:1033     #1  0x00007f761c31660e in virQEMUDriverCreateCapabilities (driver=driver@entry=0x7f7614111060)         at qemu/qemu_conf.c:1043     #2  0x00007f761c3168b3 in virQEMUDriverGetCapabilities (driver=0x7f7614111060,         refresh=<optimized out>) at qemu/qemu_conf.c:1103     #3  0x00007f761c334d16 in qemuMigrationCookieXMLParse (flags=32, ctxt=0x7f76040040c0,         doc=0x7f76040425c0, driver=0x7f7614111060, mig=0x7f760400ee10)         at qemu/qemu_migration_cookie.c:1209     #4  qemuMigrationCookieXMLParseStr (flags=32,         xml=0x7f7604004580 "<qemu-migration>\n  <name>519ed304-375a-4819-a2d5-2f0ba662b9bc</name>         049152ab-efdf-4aaf-ab08-b57ac1816351</uuid>         <hostname>gongwei-nestedcluster-20210330042359-1</me>         <hostuuid>41d69"..., driver=0x7f7614111060, mig=0x7f760400ee10)         at qemu/qemu_migration_cookie.c:1404     #5  qemuMigrationEatCookie (driver=driver@entry=0x7f7614111060, dom=dom@entry=0x7f7604001ac0,         cookiein=cookiein@entry=0x7f7604004580 "<qemu-migration>         <name>519ed304-375a-4819-a2d5-2f09bc</name>         <uuid>049152ab-efdf-4aaf-ab08-b57ac1816351</uuid>         <hostname>gongwei-nestedcluste0330042359-1</hostname>         <hostuuid>41d69"..., cookieinlen=cookieinlen@entry=1410,         flags=flags@entry=32) at qemu/qemu_migration_cookie.c:1501     #6  0x00007f761c3291d5 in qemuMigrationSrcConfirmPhase (driver=driver@entry=0x7f7614111060,         vm=vm@entry=0x7f7604001ac0,         cookiein=0x7f7604004580 "<qemu-migration>         <name>519ed304-375a-4819-a2d5-2f0ba662b9bc</nameuuid>049152ab-efdf-4aaf-ab08-b57ac1816351</uuid>         <hostname>gongwei-nestedcluster-2021033004235ostname>         <hostuuid>41d69"..., cookieinlen=1410, flags=14875, retcode=retcode@entry=0)         at qemu/qemu_migration.c:2805     #7  0x00007f761c331539 in qemuMigrationSrcPerformPeer2Peer3 (flags=14875, useParams=true,         bandwidth=0, migParams=0x7f760400f070, nbdPort=0, migrate_disks=<optimized out>,         nmigrate_disks=0, listenAddress=<optimized out>, graphicsuri=<optimized out>,         uri=<optimized out>, dname=0x0, persist_xml=0x0, xmlin=<optimized out>, vm=0x7f7604001ac0,         dconnuri=0x7f7604000df0 "qemu+tcp://10.181.177.170/system", dconn=0x7f7604021680,         sconn=0x7f7608001410, driver=0x7f7614111060) at qemu/qemu_migration.c:4202     (gdb) frame 1     #1  0x00007f761c31660e in virQEMUDriverCreateCapabilities (driver=driver@entry=0x7f7614111060)         at qemu/qemu_conf.c:1043     1043     if (!(sec_managers = qemuSecurityGetNested(driver->securityManager)))     (gdb) p *(driver->securityManager)     $2 = {parent = {parent = {u = {dummy_align1 = 140145119544368, dummy_align2 = 0x7f7614114430, s =           magic = 336675888, refs = 32630}}, klass = 0xdeadbeef}, lock = {lock = {__data = {           __lock = 0, __count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins = 0, __elision           __list = {__prev = 0x0, __next = 0x0}}, __size = '\000' <repeats 39 times>, __align = 0           drv = 0x0, flags = 0, virtDriver = 0x0, privateData = 0x0}     if (STREQ("stack", mgr->drv->name)  mgr->drv is 0x0 Signed-off-by: gongwei <gongwei(a)smartx.com&gt; --- src/security/security_manager.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/security/security_manager.c b/src/security/security_manager.c index d8b84e2861..96ca9ee861 100644 --- a/src/security/security_manager.c +++ b/src/security/security_manager.c @@ -1030,6 +1030,9 @@ virSecurityManagerGetNested(virSecurityManager *mgr) {      virSecurityManager ** list = NULL; +    if (mgr == NULL || mgr->drv == NULL) +        return NULL; +      if (STREQ("stack", mgr->drv->name))          return virSecurityStackGetNested(mgr); -- 2.24.1