From: Dmitry Safonov <dima@arista.com>
To: Jiri Slaby <jslaby@suse.cz>, linux-kernel@vger.kernel.org
Cc: "Daniel Axtens" <dja@axtens.net>,
"Dmitry Safonov" <0x7f454c46@gmail.com>,
"Sergey Senozhatsky" <sergey.senozhatsky.work@gmail.com>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Tan Xiaojun" <tanxiaojun@huawei.com>,
"Peter Hurley" <peter@hurleysoftware.com>,
"Pasi Kärkkäinen" <pasik@iki.fi>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Michael Neuling" <mikey@neuling.org>,
"Mikulas Patocka" <mpatocka@redhat.com>
Subject: Re: [PATCH 3/4] tty: Lock tty pair in tty_init_dev()
Date: Wed, 29 Aug 2018 17:28:31 +0100 [thread overview]
Message-ID: <1535560111.23560.61.camel@arista.com> (raw)
In-Reply-To: <22935dc9-a9fe-5fc8-4c97-3f5c7b07b8c3@suse.cz>
On Wed, 2018-08-29 at 16:46 +0200, Jiri Slaby wrote:
> On 08/29/2018, 04:23 AM, Dmitry Safonov wrote:
> > It's safe to not lock both here - done to silence attempt lockdep
> > assert in
> > tty_ldisc_open(), which will be added with following patch.
>
> SOrry, could you elaborate here? I don't follow...
Sure, 4/4 patch adds lockdep_assert_held() into tty_ldisc_open().
Currently ldisc in tty->link isn't locked, which according to code
shouldn't be an issue, as far as I can see.
So, this patch silences lockdep warining by holding the semaphore,
which is slowpath anyway and doesn't case any new contention.
(actually, not holding the semaphore for slave might be an issue if one
opens slave before it's fully initialized, but I'm not sure if it's
possible).
--
Thanks,
Dmitry
next prev parent reply other threads:[~2018-08-29 16:28 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-29 2:23 [PATCH 0/4] tty: Hold write ldisc sem in tty_reopen() Dmitry Safonov
2018-08-29 2:23 ` [PATCH 1/4] tty: Drop tty->count on tty_reopen() failure Dmitry Safonov
2018-08-29 14:38 ` Jiri Slaby
2018-08-29 16:13 ` Dmitry Safonov
2018-08-31 6:47 ` Jiri Slaby
2018-08-31 11:54 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 2/4] tty: Hold tty_ldisc_lock() during tty_reopen() Dmitry Safonov
2018-08-29 4:34 ` Sergey Senozhatsky
2018-08-29 14:30 ` Dmitry Safonov
2018-08-30 5:16 ` Benjamin Herrenschmidt
2018-08-29 14:40 ` Jiri Slaby
2018-08-29 14:45 ` Jiri Slaby
2018-08-29 16:36 ` Dmitry Safonov
2018-08-29 15:19 ` Tetsuo Handa
2018-08-31 6:51 ` Jiri Slaby
2018-08-31 11:17 ` Tetsuo Handa
2018-08-31 11:21 ` Jiri Slaby
2018-08-31 12:12 ` Dmitry Safonov
2018-09-07 4:50 ` [LKP] [tty] 0b4f83d510: INFO:task_blocked_for_more_than#seconds kernel test robot
2018-09-07 6:39 ` Jiri Slaby
2018-09-07 11:12 ` Dmitry Safonov
2018-09-10 5:14 ` Sergey Senozhatsky
2018-09-10 18:50 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 3/4] tty: Lock tty pair in tty_init_dev() Dmitry Safonov
2018-08-29 14:46 ` Jiri Slaby
2018-08-29 16:28 ` Dmitry Safonov [this message]
2018-08-31 6:54 ` Jiri Slaby
2018-08-31 12:22 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 4/4] tty/lockdep: Add ldisc_sem asserts Dmitry Safonov
2018-08-30 7:03 ` [PATCH 0/4] tty: Hold write ldisc sem in tty_reopen() Pasi Kärkkäinen
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