Re: [PATCH] c/r: piggyback on task->saved_sigmask and drop task->checkpoint_data

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
> The field task->checkpoint_data was introduced to hold the saved
> mask of a task so that it could be restored last thing before a
> task returns to userspace.
> 
> Given that we can piggyback on the existing task->saved_sigmask field,
> this patch drops the special checkpoint_data pointer.
> 
> Signed-off-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>

Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

I love dropping tsk->checkpoint_data.

This doesn't address the possibility that we might need to actually
checkpoint the saved_sigmask instead of blocked in certain cases,
of course, I assume that would come in a later patch?

-serge

> ---
>  checkpoint/process.c             |   18 ++----------------
>  checkpoint/signal.c              |    4 ++--
>  include/linux/checkpoint_types.h |    4 ----
>  include/linux/sched.h            |    1 -
>  4 files changed, 4 insertions(+), 23 deletions(-)
> 
> diff --git a/checkpoint/process.c b/checkpoint/process.c
> index 94cd0c1..f917112 100644
> --- a/checkpoint/process.c
> +++ b/checkpoint/process.c
> @@ -858,11 +858,6 @@ int pre_restore_task(void)
>  {
>  	sigset_t sigset;
> 
> -	/* task-specific restart data: freed from post_restore_task() */
> -	current->checkpoint_data = kzalloc(sizeof(struct ckpt_data), GFP_KERNEL);
> -	if (!current->checkpoint_data)
> -		return -ENOMEM;
> -
>  	/*
>  	 * Block task's signals to avoid interruptions due to signals,
>  	 * say, from restored timers, file descriptors etc. Signals
> @@ -872,8 +867,7 @@ int pre_restore_task(void)
>  	 * i/o notification may fail the restart if a signal occurs
>  	 * before that task completed its restore. FIX ?
>  	 */
> -
> -	current->checkpoint_data->blocked = current->blocked;
> +	current->saved_sigmask = current->blocked;
> 
>  	sigfillset(&sigset);
>  	sigdelset(&sigset, SIGKILL);
> @@ -886,16 +880,8 @@ int pre_restore_task(void)
>  /* finish up task restore */
>  void post_restore_task(void)
>  {
> -	/* can happen if restart failed early */
> -	if (!current->checkpoint_data)
> -		return;
> -
>  	/* only now is it safe to unblock the restored task's signals */
> -	sigprocmask(SIG_SETMASK, &current->checkpoint_data->blocked, NULL);
> -
> -	/* task-specific restart data: allocated in pre_restore_task() */
> -	kfree(current->checkpoint_data);
> -	current->checkpoint_data = NULL;
> +	sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
>  }
> 
>  /* read the entire state of the current task */
> diff --git a/checkpoint/signal.c b/checkpoint/signal.c
> index 609e924..d448278 100644
> --- a/checkpoint/signal.c
> +++ b/checkpoint/signal.c
> @@ -719,10 +719,10 @@ int restore_task_signal(struct ckpt_ctx *ctx)
> 
>  	/*
>  	 * Unblocking signals now may affect us in wait_task_sync().
> -	 * Instead, save blocked mask in current->checkpoint_data for
> +	 * Instead, save blocked mask in current->saved_sigmaks for
>  	 * post_restore_task().
>  	 */
> -	current->checkpoint_data->blocked = blocked;
> +	current->saved_sigmask = blocked;
> 
>  	ckpt_hdr_put(ctx, h);
>  	return 0;
> diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
> index 51efd5a..5d5e00d 100644
> --- a/include/linux/checkpoint_types.h
> +++ b/include/linux/checkpoint_types.h
> @@ -29,10 +29,6 @@ struct ckpt_stats {
>  	int user_ns;
>  };
> 
> -struct ckpt_data {
> -	sigset_t blocked;
> -};
> -
>  struct ckpt_ctx {
>  	int crid;		/* unique checkpoint id */
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 965b6c6..a70d7d1 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1584,7 +1584,6 @@ struct task_struct {
>  #endif
>  #ifdef CONFIG_CHECKPOINT
>  	struct ckpt_ctx *checkpoint_ctx;
> -	struct ckpt_data *checkpoint_data;
>  #endif
>  };
> 
> -- 
> 1.6.3.3
> 
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