From: Peter Krempa <pkrempa@xxxxxxxxxx> Successful return from 'virConnectDomainEventDeregisterAny' does not guarantee that there aren't still in-progress events being handled by the callbacks. Since 'cmdEvent' passes in a slice from an array as the private data of the callbacks, we must ensure that the array stays in scope (it's auto-freed) for the whole time there are possible callbacks being executed. While in practice this doesn't happen as the callbacks are usually quick enough to finish while unregistering stuff, placing a 'sleep(1)' into e.g. 'virshEventLifecyclePrint' and starting a domain results in crash of virsh with the following backtrace: Program terminated with signal SIGSEGV, Segmentation fault. #0 0x00005557b5cfd343 in virshEventPrintf (data=data@entry=0x5557db9619b0, fmt=fmt@entry=0x5557b5d5e527 "%s") at ../../../libvirt/tools/virsh-domain-event.c:252 Thread 2 (Thread 0x7f59a54b7d00 (LWP 2097121)): #0 0x00007f59a6cadbf9 in __futex_abstimed_wait_common () at /lib64/libc.so.6 #1 0x00007f59a6cb2cf3 in __pthread_clockjoin_ex () at /lib64/libc.so.6 #2 0x00005557b5cd57f6 in virshDeinit (ctl=0x7ffc7b615140) at ../../../libvirt/tools/virsh.c:408 #3 0x00005557b5cd5391 in main (argc=<optimized out>, argv=<optimized out>) at ../../../libvirt/tools/virsh.c:932 Thread 1 (Thread 0x7f59a51a66c0 (LWP 2097122)): #0 0x00005557b5cfd343 in virshEventPrintf (data=data@entry=0x5557db9619b0, fmt=fmt@entry=0x5557b5d5e527 "%s") at ../../../libvirt/tools/virsh-domain-event.c:252 #1 0x00005557b5cffa10 in virshEventPrint (data=0x5557db9619b0, buf=0x7f59a51a55c0) at ../../../libvirt/tools/virsh-domain-event.c:290 #2 virshEventLifecyclePrint (conn=<optimized out>, dom=<optimized out>, event=<optimized out>, detail=<optimized out>, opaque=0x5557db9619b0) at ../../../libvirt/ [snipped]
