[Cluster-devel] [PATCH] glocktop: Fix a tight loop under nohup

[Bob Peterson]

----- Original Message -----
> When glocktop is run under nohup, it redirects /dev/null to stdin, which
> flags up EOF and causes the file descriptor to always be in a ready
> state when select()ed. This causes select() to return immediately
> instead of timing out after the refresh delay.
> 
> Make sure to sleep for the refresh delay on EOF to avoid getting into a
> tight loop when running under nohup.
> 
> Signed-off-by: Andrew Price <anprice at redhat.com>
> ---
>  gfs2/glocktop/glocktop.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/gfs2/glocktop/glocktop.c b/gfs2/glocktop/glocktop.c
> index 43c3c3f..fe6bcc2 100644
> --- a/gfs2/glocktop/glocktop.c
> +++ b/gfs2/glocktop/glocktop.c
> @@ -1856,6 +1856,15 @@ int main(int argc, char **argv)
>  				if (refresh_time < 1)
>  					refresh_time = 1;
>  				break;
> +			/* We can get an EOF if the user hits ^D or if
> +			   /dev/null is redirected to stdin, such as when
> +			   running under nohup. It should be safe to assume the
> +			   latter since ^D shouldn't be expected to do anything
> +			   useful. In that case, select() returns immediately
> +			   so we need to enforce the refresh delay with a sleep */
> +			case EOF:
> +				sleep(refresh_time);
> +				break;
>  			}
>  		}
>  		iters_done++;
> --
> 2.4.3
> 
> 

ACK

Bob Peterson