[Patch] weston-launch: Fix tight poll/recvmsg loop on weston exit

[Derek Foreman]

Still need to decide what to do with this patch...

comments below.

On 14/05/15 03:43 PM, Derek Foreman wrote:
> On 27/03/15 07:29 AM, Bruno Prémont wrote:
>> When weston fails to run while being launched by weston-launch it's
>> socketpair causes poll() to notify POLLIN|POLLHUP and lets recvmsg()
>> return 0.
>>
>> Properly cleanup and exit in that case instead of poll()ing in a tight
>> loop and leaving tty in graphics mode if we get SIGKILLed as only way
>> out.
>>
>> This happens only when weston-launch (and weston) are being traced
>> as in `strace -f weston-launch` as then signalfd is not passing the
>> SIGCHLD signal.
> 
> How would I go about reproducing this bug?
> 
> When I strace -f weston-launch sigchild gets through just fine.
> 
>>
>> Signed-off-by: Bruno Prémont <bonbons at linux-vserver.org>
>> ---
>> --- a/src/weston-launch.c	2015-03-01 18:46:27.289835438 +0100
>> +++ b/src/weston-launch.c	2015-03-01 18:46:24.599835453 +0100
>> @@ -771,6 +771,8 @@ main(int argc, char *argv[])
>>  			error(0, errno, "poll failed");
>>  		if (fds[0].revents & POLLIN)
>>  			handle_socket_msg(&wl);
>> +		if (fds[0].revents & POLLHUP)
>> +			quit(&wl, 0);

This would prevent us from getting weston's exit code on a successful
exit, since it could trigger before the sigchild handling?

Just moving the clause after the fds[1] test isn't sufficient to fix
that as it could happen in an earlier event before sigchld even happens.

It would be good if you could explain how exactly to reproduce the problem.

>>  		if (fds[1].revents)
>>  			handle_signal(&wl);
>>  	}
>>
>>
>>
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> 
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