Ad pointed out by Dan Berrange:
So if some thread in libvirtd is currently executing a logging call,
while another thread calls virExec(), that other thread no longer
exists in the child, but its lock is never released. So when the
child then does virLogReset() it deadlocks.
The only way I see to address this, is for the parent process to call
virLogLock(), immediately before fork(), and then virLogUnlock()
afterwards in both parent & child. This will ensure that no other
thread
can be holding the lock across fork().
* src/util/logging.[ch] src/libvirt_private.syms: export virLogLock() and
virLogUnlock()
* src/util/util.c: lock just before forking and unlock just after - in
both parent and child.
When configuring logging settings, keep more information about the
output destination. Add accessors to retrieve the filter and output
settings in the original string form; this to be used to set up
environment for a child process that also logs.
* src/util/logging.[ch]: add virLogGetFilters and virLogGetOutputs
accessors and modify the internals (including virLogDefineOutput())
to save the data needed for the accessors
