[CRIU] [PATCH 3/8] sig: Instantly drop SA_NOCLDSTOP for swrk_restore

[Andrew Vagin]

Acked-by: Andrew Vagin <avagin at parallels.com>

On Wed, Aug 06, 2014 at 04:24:36PM +0400, Pavel Emelyanov wrote:
> We tune the CHLD handler if we're restoring root task
> as sibling. This tuning is better to be done with one
> sigaction() call, rather than two. First, it's shorter
> and the second -- it will allow us to move the whole
> criu signalling setup into one helper.
> 
> Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
> ---
>  cr-restore.c | 29 ++++++++++++-----------------
>  1 file changed, 12 insertions(+), 17 deletions(-)
> 
> diff --git a/cr-restore.c b/cr-restore.c
> index e34e8a6..5aa5472 100644
> --- a/cr-restore.c
> +++ b/cr-restore.c
> @@ -1498,6 +1498,18 @@ static int restore_root_task(struct pstree_item *init)
>  	}
>  
>  	act.sa_flags |= SA_NOCLDSTOP | SA_SIGINFO | SA_RESTART;
> +	if (opts.swrk_restore)
> +		/*
> +		 * Root task will be our sibling. This means, that
> +		 * we will not notice when (if) it dies in SIGCHLD
> +		 * handler, but we should. To do this -- attach to
> +		 * the guy with ptrace (below) and (!) make the kernel
> +		 * deliver us the signal when it will get stopped.
> +		 * It will in case of e.g. segfault before handling
> +		 * the signal.
> +		 */
> +		act.sa_flags &= ~SA_NOCLDSTOP;
> +
>  	act.sa_sigaction = sigchld_handler;
>  	sigemptyset(&act.sa_mask);
>  	sigaddset(&act.sa_mask, SIGCHLD);
> @@ -1545,23 +1557,6 @@ static int restore_root_task(struct pstree_item *init)
>  		return -1;
>  
>  	if (opts.swrk_restore) {
> -		/*
> -		 * Root task is not our sibling. This means, that
> -		 * we will not notice when (if) it dies in SIGCHLD
> -		 * handler, but we should. To do this -- attach to
> -		 * the guy with ptrace and (!) make the kernel
> -		 * deliver us the signal when it will get stopped.
> -		 * It will in case of e.g. segfault before handling
> -		 * the signal.
> -		 */
> -
> -		act.sa_flags &= ~SA_NOCLDSTOP;
> -		ret = sigaction(SIGCHLD, &act, NULL);
> -		if (ret < 0) {
> -			pr_perror("sigaction() failed");
> -			goto out;
> -		}
> -
>  		if (ptrace(PTRACE_SEIZE, init->pid.real, 0, 0)) {
>  			pr_perror("Can't attach to init");
>  			goto out;
> -- 
> 1.8.4.2
> 
> 
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