linux-kernel - Re: [PATCH] kernel/hung_task.c: export sysctl_hung_task_timeout

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Message-Id: <20240209141324.28cae36fe14c909058c1fed7@linux-foundation.org>
Date: Fri, 9 Feb 2024 14:13:24 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: linux-kernel@...r.kernel.org, fuyuanli <fuyuanli@...iglobal.com>
Subject: Re: [PATCH] kernel/hung_task.c: export
 sysctl_hung_task_timeout_secs

On Fri,  9 Feb 2024 02:09:35 -0500 Kent Overstreet <kent.overstreet@...ux.dev> wrote:

> needed for thread_with_file; also rare but not unheard of to need this
> in module code, when blocking on user input.

I see no bcachefs code in linux-next which uses this.  All I have to go
with is the above explanation-free assertion.  IOW this patch is
unreviewable.

> one workaround used by some code is wait_event_interruptible()

examples?

> - but that can be buggy if the outer context isn't expecting unwinding.

More explanation of this?

> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -43,6 +43,7 @@ static int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
>   * Zero means infinite timeout - no checking done:
>   */
>  unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
> +EXPORT_SYMBOL_GPL(sysctl_hung_task_timeout_secs);

It seems strange that a module wouild want this.  Makes one wonder what
the heck is going on in there.