linux-kernel - Re: [PATCH 2/8] kernel: unmask SIGSTOP for IO threads

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Date:   Fri, 26 Mar 2021 14:48:41 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     io-uring@...r.kernel.org, torvalds@...ux-foundation.org,
        ebiederm@...ssion.com, metze@...ba.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] kernel: unmask SIGSTOP for IO threads

Jens, sorry, I got lost :/

On 03/25, Jens Axboe wrote:
>
> With IO threads accepting signals, including SIGSTOP,

where can I find this change? Looks like I wasn't cc'ed...

> unmask the
> SIGSTOP signal from the default blocked mask.
> 
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> ---
>  kernel/fork.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d3171e8e88e5..d5a40552910f 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2435,7 +2435,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
>  	tsk = copy_process(NULL, 0, node, &args);
>  	if (!IS_ERR(tsk)) {
>  		sigfillset(&tsk->blocked);
> -		sigdelsetmask(&tsk->blocked, sigmask(SIGKILL));
> +		sigdelsetmask(&tsk->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));

siginitsetinv(blocked, sigmask(SIGKILL)|sigmask(SIGSTOP)) but this is minor.

To remind, either way this is racy and can't really help.

And if "IO threads accepting signals" then I don't understand why. Sorry,
I must have missed something.

Oleg.