From: Xie He <xie.he.0141@gmail.com>
To: Gao Yan <gao.yanB@h3c.com>
Cc: paulus@samba.org, davem@davemloft.net, kuba@kernel.org,
linux-ppp@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: remove disc_data_lock in ppp line discipline
Date: Fri, 01 Jan 2021 01:37:44 +0000 [thread overview]
Message-ID: <20210101013744.72562-1-xie.he.0141@gmail.com> (raw)
In-Reply-To: <20201228071550.15745-1-gao.yanB@h3c.com>
> In tty layer, it use tty->ldisc_sem to proect tty_ldisc_ops.
> So I think tty->ldisc_sem can also protect tty->disc_data;
It might help by CC'ing TTY people, so that we could get this reviewed by
people who are familiar with TTY code.
Greg Kroah-Hartman <gregkh@linuxfoundation.org> (supporter:TTY LAYER)
Jiri Slaby <jirislaby@kernel.org> (supporter:TTY LAYER)
Thanks!
> For examlpe,
> When cpu A is running ppp_synctty_ioctl that hold the tty->ldisc_sem,
> at the same time if cpu B calls ppp_synctty_close, it will wait until
> cpu A release tty->ldisc_sem. So I think it is unnecessary to have the
> disc_data_lock;
>
> cpu A cpu B
> tty_ioctl tty_reopen
> ->hold tty->ldisc_sem ->hold tty->ldisc_sem(write), failed
> ->ld->ops->ioctl ->wait...
> ->release tty->ldisc_sem ->wait...OK,hold tty->ldisc_sem
> ->tty_ldisc_reinit
> ->tty_ldisc_close
> ->ld->ops->close
IMHO an example might not be necessary. Examples are useful to show
incorrectness. But we cannot show correctness by examples because
examples are not exhaustive.
BTW, there're some typos:
"proect" -> "protect"
"examlpe" -> "example"
"that hold ..." -> "that holds ..."
"cpu A release ..." -> "cpu A releases ..."
> * FIXME: this is no longer true. The _close path for the ldisc is
> * now guaranteed to be sane.
> */
> *
> * FIXME: Fixed in tty_io nowadays.
> */
Since you are removing "disc_data_lock", please update (or remove) these
two comments. Thanks!
prev parent reply other threads:[~2021-01-01 1:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 7:15 [PATCH] net: remove disc_data_lock in ppp line discipline Gao Yan
2020-12-31 10:00 ` 答复: [PATCH] net: remove disc_data_lock in =?utf-8?Q?_ppp_line_discipl Gaoyan
2021-01-01 1:37 ` Xie He [this message]
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