Re: [PATCH] autofs4: Use wait_event_killable

From: Ian Kent
Date: Mon Mar 19 2018 - 21:59:17 EST


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

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@xxxxxxxxxxxxx>
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
> ---
> 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;
>
> /*
>