I just code review, found there may be problem.
The follow statement in founction qemuProcessReconnectHelper:
"if (virThreadCreate(&thread, false, qemuProcessReconnect, data) < 0) "
may be failed (no one can guarantee 'virThreadCreate' always success).
if ‘virThreadCreate’ failed, the follow backstrace we will get:
#0 0x00007fa89921203e in pthread_rwlock_wrlock () from /lib64/libpthread.so.0
#1 0x00007fa89ba218e5 in virRWLockWrite (m=<optimized out>) at util/virthread.c:122
#2 0x00007fa89b9f9ebb in virObjectRWLockWrite (anyobj=<optimized out>) at util/virobject.c:487
#3 0x00007fa89ba82a68 in virDomainObjListRemove (doms=0x7fa87411fde0, dom=0x7fa8740f94f0) at conf/virdomainobjlist.c:400
#4 0x00007fa87e1b9ace in qemuDomainRemoveInactive (driver=driver@entry=0x7fa87411aa20, vm=vm@entry=0x7fa8740f94f0) at qemu/qemu_domain.c:8309
#5 0x00007fa87e1b9c02 in qemuDomainRemoveInactiveJob (driver=0x7fa87411aa20, vm=0x7fa8740f94f0) at qemu/qemu_domain.c:8331
#6 0x00007fa87e1ef36d in qemuProcessReconnectHelper (obj=0x7fa8740f94f0, opaque=0x7fa87b4b3c30) at qemu/qemu_process.c:8035
#7 0x00007fa89ba81e9a in virDomainObjListHelper (payload=<optimized out>, name=<optimized out>, opaque=0x7fa87b4b3c00) at conf/virdomainobjlist.c:804
#8 0x00007fa89b9ccaa0 in virHashForEach (table=0x7fa87410e520, iter=iter@entry=0x7fa89ba81e90 <virDomainObjListHelper>, data="">
at util/virhash.c:580
#9 0x00007fa89ba83391 in virDomainObjListForEach (doms=0x7fa87411fde0, callback=callback@entry=0x7fa87e1ef220 <qemuProcessReconnectHelper>,
opaque=opaque@entry=0x7fa87b4b3c30) at conf/virdomainobjlist.c:819
#10 0x00007fa87e1f1564 in qemuProcessReconnectAll (driver=<optimized out>) at qemu/qemu_process.c:8056
#11 0x00007fa87e227928 in qemuStateInitialize (privileged=true, callback=<optimized out>, opaque=<optimized out>) at qemu/qemu_driver.c:919
#12 0x00007fa89bb9f91f in virStateInitialize (privileged=true, callback=callback@entry=0x7fa89c547cd0 <daemonInhibitCallback>, opaque=opaque@entry=0x7fa89d875c00)
at libvirt.c:662
#13 0x00007fa89c547d2b in daemonRunStateInit (opaque=0x7fa89d875c00) at remote/remote_daemon.c:803
#14 0x00007fa89ba21712 in virThreadHelper (data="" out>) at util/virthread.c:206
#15 0x00007fa89920edc5 in start_thread () from /lib64/libpthread.so.0
#16 0x00007fa898b3673d in clone () from /lib64/libc.so.6
frame 8, virHashForEach has called virObjectLock(doms)
frame 3, virDomainObjListRemove calls virObjectRWLockWrite(doms) again.
thus deadlock occurs.
> qemuProcessReconnectHelper has hold the doms lock, if create
> qemuProcessReconnect thread failed, it will get the doms lock
> again to remove the dom from doms list.
>
> add obj->inReconnetCtx flag to avoid deadlock.
Please describe the situation more or provide a reproducer.
>
> Signed-off-by: Wang Yechao <wang.yechao255@xxxxxxxxxx>
> ---
> src/conf/domain_conf.h | 1 +
> src/conf/virdomainobjlist.c | 6 ++++--
> src/qemu/qemu_process.c | 1 +
> 3 files changed, 6 insertions(+), 2 deletions(-)
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