Re: [PATCH V3 06/22] vl: add helper to request re-exec

[Daniel P . Berrangé]

On Thu, May 13, 2021 at 04:19:22PM -0400, Steven Sistare wrote:
> On 5/7/2021 10:31 AM, Eric Blake wrote:
> > On 5/7/21 7:25 AM, Steve Sistare wrote:
> >> Add a qemu_exec_requested() hook that causes the main loop to exit and
> >> re-exec qemu using the same initial arguments.  If /usr/bin/qemu-exec
> >> exists, exec that instead.  This is an optional site-specific trampoline
> >> that may alter the environment before exec'ing the qemu binary.
> >>
> >> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> >> ---
> > 
> >> +static void qemu_exec(void)
> >> +{
> >> +    const char *helper = "/usr/bin/qemu-exec";
> >> +    const char *bin = !access(helper, X_OK) ? helper : argv_main[0];
> > 
> > Reads awkwardly; I would have used '...= access(helper, X_OK) == 0 ?...'
> 
> Will fix.
> 
> >> +
> >> +    execvp(bin, argv_main);
> >> +    error_report("execvp failed, errno %d.", errno);
> > 
> > error_report should not be used with a trailing dot.  
> 
> Will fix.  I was not sure because I see examples both ways, though no dot 
> prevails.
> Perhaps it should be added to the style guide and checkpatch.
> 
> > Also, %d for errno is awkward, better is:
> > 
> > error_report("execvp failed: %s", strerror(errno));
> 
> I shy away from strerror because it is not thread safe, but I see qemu uses it
> extensively.  Will fix.

GLib provides  'g_strerror' which is threadsafe, but without
the horrible API of strerror_r.  It works by caching the
errno strings in a static table on demand.  We don't use
it much in QEMU, but I think we ought to.


Regards,
Daniel
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