Re: [PATCH v3 2/2] tests: add pidfd poll tests

[Joel Fernandes <joel@joelfernandes.org>]

On Fri, Jul 26, 2019 at 09:22:26AM -0700, Suren Baghdasaryan wrote:
> This adds testing for polling on pidfd of a process being killed. Test runs
> 10000 iterations by default to stress test pidfd polling functionality.
> It accepts an optional command-line parameter to override the number or
> iterations to run.
> Specifically, it tests for:
> - pidfd_open on a child process succeeds
> - pidfd_send_signal on a child process succeeds
> - polling on pidfd succeeds and returns exactly one event
> - returned event is POLLIN
> - event is received within 3 secs of the process being killed
> 
> 10000 iterations was chosen because of the race condition being tested
> which is not consistently reproducible but usually is revealed after less
> than 2000 iterations.
> Reveals race fixed by commit b191d6491be6 ("pidfd: fix a poll race when setting exit_state")
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---

> +		close(pidfd);
> +		// Wait for child to prevent zombies

Comment style should be /* */, but I think Christian would be kind enough to
fix that when he applies the patch so shouldn't need a resend.

Thanks Suren and Christian!

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>