linux-kernel - Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info

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Date: Fri, 23 Feb 2024 21:41:21 +0800
From: Wen Yang <wenyang.linux@...mail.com>
To: Oleg Nesterov <oleg@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
 Christian Brauner <brauner@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info



On 2024/2/23 18:50, Oleg Nesterov wrote:
> get_signal() uses signr or ksig->info.si_signo in a chaotic way, this
> looks confusing. Change it to always use signr.
> 
> This allows us to simplify the SIGNAL_GROUP_EXIT/group_exec_task branch,
> it no longer needs to touch ksig at all.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>   kernel/signal.c | 15 +++++++++------
>   1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/signal.c b/kernel/signal.c
> index c9c57d053ce4..690982e6595e 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2727,12 +2727,15 @@ bool get_signal(struct ksignal *ksig)
>   		/* Has this task already been marked for death? */
>   		if ((signal->flags & SIGNAL_GROUP_EXIT) ||
>   		     signal->group_exec_task) {
> -			clear_siginfo(&ksig->info);
> -			ksig->info.si_signo = signr = SIGKILL;
> +			signr = SIGKILL;
>   			sigdelset(&current->pending.signal, SIGKILL);
>   			trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
> -				&sighand->action[SIGKILL - 1]);
> +					     &sighand->action[SIGKILL - 1]);
>   			recalc_sigpending();
> +			/*
> +			 * implies do_group_exit(), no need to initialize
> +			 * ksig->info
> +			 */
>   			goto fatal;

There is little question:
If the this conditions is met:
    current->flags & PF_USER_WORKER
It may execute “goto out“ instead of do_group_exit().

--
Best wishes,
Wen


>   		}
>   
> @@ -2842,7 +2845,7 @@ bool get_signal(struct ksignal *ksig)
>   				spin_lock_irq(&sighand->siglock);
>   			}
>   
> -			if (likely(do_signal_stop(ksig->info.si_signo))) {
> +			if (likely(do_signal_stop(signr))) {
>   				/* It released the siglock.  */
>   				goto relock;
>   			}
> @@ -2866,7 +2869,7 @@ bool get_signal(struct ksignal *ksig)
>   
>   		if (sig_kernel_coredump(signr)) {
>   			if (print_fatal_signals)
> -				print_fatal_signal(ksig->info.si_signo);
> +				print_fatal_signal(signr);
>   			proc_coredump_connector(current);
>   			/*
>   			 * If it was able to dump core, this kills all
> @@ -2890,7 +2893,7 @@ bool get_signal(struct ksignal *ksig)
>   		/*
>   		 * Death signals, no core dump.
>   		 */
> -		do_group_exit(ksig->info.si_signo);
> +		do_group_exit(signr);
>   		/* NOTREACHED */
>   	}
>   	spin_unlock_irq(&sighand->siglock);