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SubjectRe: [PATCH v3 16/23] tty: Make core responsible for synchronizing its work
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On Tue, 2013-02-05 at 15:20 -0500, Peter Hurley wrote:
> The tty core relies on the ldisc layer for synchronizing destruction
> of the tty. Instead, the final tty release must wait for any pending tty
> work to complete prior to tty destruction.
>
> Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
> ---
> drivers/tty/tty_io.c | 17 +++++++++++++++++
> drivers/tty/tty_ldisc.c | 24 ++++--------------------
> 2 files changed, 21 insertions(+), 20 deletions(-)

...

> diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
> index e0fdfec..c2837b2 100644
> --- a/drivers/tty/tty_ldisc.c
> +++ b/drivers/tty/tty_ldisc.c
> @@ -499,18 +499,6 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
> }
>
> /**
> - * tty_ldisc_flush_works - flush all works of a tty
> - * @tty: tty device to flush works for
> - *
> - * Sync flush all works belonging to @tty.
> - */
> -static void tty_ldisc_flush_works(struct tty_struct *tty)
> -{
> - flush_work(&tty->SAK_work);
> - flush_work(&tty->hangup_work);
> -}
> -
> -/**
> * tty_ldisc_wait_idle - wait for the ldisc to become idle
> * @tty: tty to wait for
> * @timeout: for how long to wait at most
> @@ -726,13 +714,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
> retval = tty_ldisc_halt(tty, o_tty, &work, &o_work, 5 * HZ);
>
> /*
> - * Wait for ->hangup_work to terminate.
> + * Wait for hangup to complete, if pending.
> * We must drop the mutex here in case a hangup is also in process.
> */
>
> mutex_unlock(&tty->ldisc_mutex);
>
> - tty_ldisc_flush_works(tty);
> + flush_work(&tty->hangup_work);

Careful review will note that I dropped waiting for SAK. That's because
it makes no sense to wait for SAK_work here -- ie., while setting a new
ldisc. The SAK work can just as easily run at the completion of
tty_set_ldisc() at tty_unlock().

I believe this is an artifact of the formerly shared code.

But maybe I should note that in the commit message?




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