Re: [PATCH 1/1] vircommand.c: write child pidfile before process tuning in virExec()

When VIR_EXEC_DAEMON is true and cmd->pidfile exists, the parent will expect the pidfile to be written before exiting, sitting tight in a saferead() call waiting. The child then does process tuning (via virProcessSet* functions) before writing the pidfile. Problem is that these tunings can fail, and trigger a 'fork_error' jump, before cmd->pidfile is written. The result is that the process was aborted in the child, but the parent is still hang in the saferead() call. This behavior can be reproduced by trying to create and execute a QEMU guest in user mode (e.g. using qemu:///session as non-root). virProcessSetMaxMemLock() will fail if the spawned libvirtd user process does not have CAP_SYS_RESOURCE capability. setrlimit() will fail, and a 'fork_error' jump is triggered before cmd->pidfile is written. The parent will hung in saferead() indefinitely. From the user perspective, 'virsh start <guest>' will hang up indefinitely. CTRL+C can be used to retrieve the terminal, but any subsequent 'virsh' call will also hang because the previous libvirtd user process is still there. We can fix this by moving all virProcessSet*() tuning functions to be executed after cmd->pidfile is taken care of. In the case mentioned above, this would be the result of 'virsh start' after this patch: error: Failed to start domain vm1 error: internal error: Process exited prior to exec: libvirt: error : cannot limit locked memory to 79691776: Operation not permitted Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1882093 Signed-off-by: Daniel Henrique Barboza <danielhb413(a)gmail.com&gt; --- src/util/vircommand.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)