Re: [PATCH v3] kernel/signal: Signal-based pre-coredump notification

[Oleg Nesterov <oleg@redhat.com>]

On 10/23, Enke Chen wrote:
>
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -590,6 +590,12 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>  	if (retval < 0)
>  		goto fail_creds;
>
> +	/*
> +	 * Send the pre-coredump signal to the parent if requested.
> +	 */
> +	do_notify_parent_predump();
> +	cond_resched();

I am still not sure cond_resched() makes any sense here...

> @@ -1553,6 +1553,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
>  	tty_audit_fork(sig);
>  	sched_autogroup_fork(sig);
>
> +	/* Clear the pre-coredump signal for the child */
> +	sig->predump_signal = 0;

No need, copy_signal() does zalloc().


> +void do_notify_parent_predump(void)
> +{
> +	struct sighand_struct *sighand;
> +	struct kernel_siginfo info;
> +	struct task_struct *parent;
> +	unsigned long flags;
> +	int sig;
> +
> +	read_lock(&tasklist_lock);
> +	parent = current->parent;
> +	sig = parent->signal->predump_signal;
> +	if (sig != 0) {
> +		clear_siginfo(&info);
> +		info.si_pid = task_tgid_vnr(current);
> +		info.si_signo = sig;
> +		if (sig == SIGCHLD)
> +			info.si_code = CLD_PREDUMP;
> +
> +		sighand = parent->sighand;
> +		spin_lock_irqsave(&sighand->siglock, flags);
> +		__group_send_sig_info(sig, &info, parent);
> +		spin_unlock_irqrestore(&sighand->siglock, flags);

You can just use do_send_sig_info() and remove sighand/flags/spin_lock_irqsave.

Perhaps the "likely" predump_signal==0 check at the start makes sense to avoid
read_lock(tasklist).

And I'd suggest to move it into coredump.c and make it static. It won't have
another user.

Oleg.