[PATCH 6/9] signal: Always call do_notify_parent_cldstop with siglock held

[Peter Zijlstra]

On Tue, Apr 26, 2022 at 05:52:08PM -0500, Eric W. Biederman wrote:
> Now that siglock keeps tsk->parent and tsk->real_parent constant
> require that do_notify_parent_cldstop is called with tsk->siglock held
> instead of the tasklist_lock.
> 
> As all of the callers of do_notify_parent_cldstop had to drop the
> siglock and take tasklist_lock this simplifies all of it's callers.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
> ---
>  kernel/signal.c | 156 +++++++++++++++++-------------------------------
>  1 file changed, 55 insertions(+), 101 deletions(-)
> 
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 72d96614effc..584d67deb3cb 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2121,11 +2121,13 @@ static void do_notify_parent_cldstop(struct task_struct *tsk,
>  				     bool for_ptracer, int why)
>  {
>  	struct kernel_siginfo info;
> -	unsigned long flags;
>  	struct task_struct *parent;
>  	struct sighand_struct *sighand;
> +	bool lock;
>  	u64 utime, stime;
>  
> +	assert_spin_locked(&tsk->sighand->siglock);

lockdep_assert_held() please...