Re: [libvirt] [PATCH] qemu: fix libvirtd crash when querying halted cpus info

On 02.11.2016 16:56, Maxim Nestratov wrote: > It was introduced by commit 7a51d9ebb, which started to use > monitor commands without job acquiring, which is unsafe and leads > to simultaneous access to vm->mon structure by different threads. > > Crash backtrace is the following (shortened): > > Program received signal SIGSEGV, Segmentation fault. > qemuMonitorSend (mon=mon@entry=0x7f4ef4000d20, msg=msg@entry=0x7f4f18e78640) at qemu/qemu_monitor.c:1011 > 1011 while (!mon->msg->finished) { > > 0 qemuMonitorSend () at qemu/qemu_monitor.c:1011 > 1 0x00007f691abdc720 in qemuMonitorJSONCommandWithFd () at qemu/qemu_monitor_json.c:298 > 2 0x00007f691abde64a in qemuMonitorJSONCommand at qemu/qemu_monitor_json.c:328 > 3 qemuMonitorJSONQueryCPUs at qemu/qemu_monitor_json.c:1408 > 4 0x00007f691abcaebd in qemuMonitorGetCPUInfo g@entry=false) at qemu/qemu_monitor.c:1931 > 5 0x00007f691ab96863 in qemuDomainRefreshVcpuHalted at qemu/qemu_domain.c:6309 > 6 0x00007f691ac0af99 in qemuDomainGetStatsVcpu at qemu/qemu_driver.c:18945 > 7 0x00007f691abef921 in qemuDomainGetStats at qemu/qemu_driver.c:19469 > 8 qemuConnectGetAllDomainStats at qemu/qemu_driver.c:19559 > 9 0x00007f693382e806 in virConnectGetAllDomainStats at libvirt-domain.c:11546 > 10 0x00007f6934470c40 in remoteDispatchConnectGetAllDomainStats at remote.c:6267 > > (gdb) p mon->msg > $1 = (qemuMonitorMessagePtr) 0x0 > > This change fixes it by calling qemuDomainRefreshVcpuHalted only when job is acquired. > > Signed-off-by: Maxim Nestratov <mnestratov(a)virtuozzo.com&gt; > --- > src/qemu/qemu_driver.c | 20 +++++++++++++------- > 1 file changed, 13 insertions(+), 7 deletions(-) [...] Argh ... this fell through the cracks when I moved the code from vcpuinfo to domstats. Thanks for catching and fixing that one.