linux-kernel - Re: [PATCH] autofs4: Use wait_event

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Date:   Tue, 20 Mar 2018 09:58:59 +0800
From:   Ian Kent <raven@...maw.net>
To:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Cc:     autofs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] autofs4: Use wait_event_killable

On 20/03/18 03:16, Matthew Wilcox wrote:
> From: Matthew Wilcox <mawilcox@...rosoft.com>

Hi Matthew,

> 
> This playing with signals to allow only fatal signals appears to predate
> the introduction of wait_event_killable(), and I'm fairly sure that
> wait_event_killable is what was meant to happen here.

Predates is an understatement, this is really, really old code.
Do I need to forward this to Al or Andrew?

> 
> Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
Signed-off-by: Ian Kent <raven@...maw.net>
> ---
>  fs/autofs4/waitq.c | 27 +--------------------------
>  1 file changed, 1 insertion(+), 26 deletions(-)
> 
> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> index a0c57c37fa21..c160e9b3aa0f 100644
> --- a/fs/autofs4/waitq.c
> +++ b/fs/autofs4/waitq.c
> @@ -19,9 +19,6 @@
>   */
>  static autofs_wqt_t autofs4_next_wait_queue = 1;
>  
> -/* These are the signals we allow interrupting a pending mount */
> -#define SHUTDOWN_SIGS	(sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
> -
>  void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
>  {
>  	struct autofs_wait_queue *wq, *nwq;
> @@ -486,29 +483,7 @@ int autofs4_wait(struct autofs_sb_info *sbi,
>  	 * wq->name.name is NULL iff the lock is already released
>  	 * or the mount has been made catatonic.
>  	 */
> -	if (wq->name.name) {
> -		/* Block all but "shutdown" signals while waiting */
> -		unsigned long shutdown_sigs_mask;
> -		unsigned long irqflags;
> -		sigset_t oldset;
> -
> -		spin_lock_irqsave(&current->sighand->siglock, irqflags);
> -		oldset = current->blocked;
> -		shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
> -		siginitsetinv(&current->blocked, shutdown_sigs_mask);
> -		recalc_sigpending();
> -		spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
> -
> -		wait_event_interruptible(wq->queue, wq->name.name == NULL);
> -
> -		spin_lock_irqsave(&current->sighand->siglock, irqflags);
> -		current->blocked = oldset;
> -		recalc_sigpending();
> -		spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
> -	} else {
> -		pr_debug("skipped sleeping\n");
> -	}
> -
> +	wait_event_killable(wq->queue, wq->name.name == NULL);

The wait event code looks like this will wake up on most any unmasked signal.
But my assumption is that TASK_KILLABLE tasks are only forwarded specific
signals ...

Is that right or am I missing something?

>  	status = wq->status;
>  
>  	/*
>