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Re: [libvirt] Strange periodic failures of the commandtest case



On Mon, Feb 14, 2011 at 12:32:18PM +0000, Daniel P. Berrange wrote:
> I'm getting periodic failures of the 'commandtest' case where the diff
> is
> 
> > DAEMON:no
> --
> < DAEMON:yes
> 
> For test cases 'test3' through to 'test15', except 'test'4. Tests 1,
> 2, 4, 16, 17, 18 are all unaffected. I can never reproduce it when
> I run just that one test case manually, but the automated builds
> I'm doing hit it > 50% of the time so it is clearly some kind of race
> condition. The line of code that's getting confused is this
> 
>     fprintf(log, "DAEMON:%s\n", getpgrp() == getsid(0) ? "yes" : "no");
> 
> but I'm not clear how this can be going wrong. Ideas ?

Hmm, this seems to occur when you run the build under cron. Under an
interactive shell  getpgrp() != getsid() by default. Under non-interactive
shell, then getpgrp() == getsid() even if we didn't ask to daemonize.
So this approach to detecting whether we're daemonized isn't reliable.

Perhaps the 'commandtest' program itself needs to call setsid()+setpgid()
before running the child processes ?

Daniel
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