Re: [PATCH] gssd: unblock DNOTIFY_SIGNAL in case it was blocked.

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Nov 11, 2008 at 09:29:29AM +1100, Neil Brown wrote:
> 
> I have a situation where rpc.gssd appears to not be working.
> Mount attempts which need to communicate with it block.
> 
> I've narrowed down the problem to that fact that all realtime signals
> have been blocked.  This means that DNOTIFY_SIGNAL (which is a
> realtime signal) is never delivered, so gssd never rescans the
> rpc_pipe/nfs directory.
> 
> I haven't figured out why the signals are blocked yet, but having
> rpc.gssd fail mysteriously in that situation isn't pleasant.
> 
> So I wonder what people think of the following patch.  It simply
> unblocks the signal.  Alternately we can check if it is blocked and
> warn - I'm not really sure of the significance of blocking all these
> signals.  Maybe it's wrong to just unblock them.

So we don't know what it is that's doing the blocking?

> As an aside, maybe we could change gssd_run to use "ppoll" rather than
> "poll".  Then it would not have to wake up every 500msec to see if it
> missed a signal. We would probably have to check kernel version was at
> least 2.6.16....

Yes. (What does glibc itself do in the ppoll library call if the kernel
doesn't support it?)

--b.

> diff --git a/utils/gssd/gssd_main_loop.c b/utils/gssd/gssd_main_loop.c
> index 84f04e9..b9f3a06 100644
> --- a/utils/gssd/gssd_main_loop.c
> +++ b/utils/gssd/gssd_main_loop.c
> @@ -99,6 +99,7 @@ gssd_run()
>  	int			ret;
>  	struct sigaction	dn_act;
>  	int			fd;
> +	sigset_t		set;
>  
>  	/* Taken from linux/Documentation/dnotify.txt: */
>  	dn_act.sa_sigaction = dir_notify_handler;
> @@ -106,6 +107,11 @@ gssd_run()
>  	dn_act.sa_flags = SA_SIGINFO;
>  	sigaction(DNOTIFY_SIGNAL, &dn_act, NULL);
>  
> +	/* just in case the signal is blocked... */
> +	sigemptyset(&set);
> +	sigaddset(&set, DNOTIFY_SIGNAL);
> +	sigprocmask(SIG_UNBLOCK, &set, NULL);
> +
>  	if ((fd = open(pipefs_nfsdir, O_RDONLY)) == -1) {
>  		printerr(0, "ERROR: failed to open %s: %s\n",
>  			 pipefs_nfsdir, strerror(errno));
> --
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