[libvirt] [PATCH 3/3] Manually kill gzip if restore fails before starting qemu

[Laine Stump]

On 01/25/2011 12:47 PM, Daniel P. Berrange wrote:
> On Tue, Jan 25, 2011 at 04:24:20AM -0500, Laine Stump wrote:
>> If a guest image is saved in compressed format, and the restore fails
>> in some way after the intermediate process used to uncompress the
>> image has been started, but before qemu has been started to hook up to
>> the uncompressor, libvirt will endlessly wait for the uncompressor to
>> finish, but it never will because it's still waiting to have something
>> hooked up to drain its output.
>>
>> The solution is to manually send a SIGTERM to the compressor process
>> before calling waitpid on it (only if the restore has failed, of
>> course).
> Are we leaking a file descriptor here then ?  I would think
> it would get EPIPE or EIO or an end-of-file if QEMU didn't
> start up and automatically exit. That we need to kill it
> seems odd (though a worthy extra measure once we're verified
> that all FDs are closed properly).

Good point. I guess the proper thing to do is first close the fd that's 
pointing to the pipe, then do the kill (which will probably be 
unnecessary, but as you say a worthy extra measure).

Do you think it's necessary to do anything this complicated?

    kill(pid, SIGTERM);
    (usleep or maybe a waitpid(pid, &childstat, WNOHANG) ?)
    if (kill(pid, 0) == 0)
       kill(pid, SIGKILL);

Or is the single SIGTERM sufficient?