[PATCH 1/3] signals: Allow generation of SIGKILL to exiting task.

[Eric W. Biederman]

Andrey Grodzovsky <andrey.grodzovsky at amd.com> writes:

> Currently calling wait_event_killable as part of exiting process
> will stall forever since SIGKILL generation is suppresed by PF_EXITING.
>
> In our partilaur case AMDGPU driver wants to flush all GPU jobs in
> flight before shutting down. But if some job hangs the pipe we still want to
> be able to kill it and avoid a process in D state.

This makes me profoundly uncomfotable.  You are changing the linux
semantics of what it means for a process to be exiting.  Functionally
this may require all kinds of changes to when we allow processes to stop
processing signals.

So without a really good thought out explanation that takes into account
all of the issues involved in process exiting and posix conformance.

Nacked-by: "Eric W. Biederman" <ebiederm at xmission.com>

Eric

> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
> ---
>  kernel/signal.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index c6e4c83..c49c706 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -886,10 +886,10 @@ static inline int wants_signal(int sig, struct task_struct *p)
>  {
>  	if (sigismember(&p->blocked, sig))
>  		return 0;
> -	if (p->flags & PF_EXITING)
> -		return 0;
>  	if (sig == SIGKILL)
>  		return 1;
> +	if (p->flags & PF_EXITING)
> +		return 0;
>  	if (task_is_stopped_or_traced(p))
>  		return 0;
>  	return task_curr(p) || !signal_pending(p);