From: Peter Zijlstra <peterz@infradead.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: "Dmitry Safonov" <dima@arista.com>,
linux-kernel@vger.kernel.org,
"Dmitry Safonov" <0x7f454c46@gmail.com>,
"Daniel Axtens" <dja@axtens.net>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Michael Neuling" <mikey@neuling.org>,
"Mikulas Patocka" <mpatocka@redhat.com>,
"Nathan March" <nathan@gt.net>, "Pasi Kärkkäinen" <pasik@iki.fi>,
"Peter Hurley" <peter@hurleysoftware.com>,
"Rong, Chen" <rong.a.chen@intel.com>,
"Tan Xiaojun" <tanxiaojun@huawei.com>,
"Tetsuo Handa" <penguin-kernel@I-love.SAKURA.ne.jp>,
stable@vger.kernel.org,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Jiri Slaby" <jslaby@suse.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCHv3 2/6] tty/ldsem: Update waiter->task before waking up reader
Date: Tue, 11 Sep 2018 13:44:29 +0200 [thread overview]
Message-ID: <20180911114429.GT24106@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180911054129.GC4065@jagdpanzerIV>
On Tue, Sep 11, 2018 at 02:41:29PM +0900, Sergey Senozhatsky wrote:
> On (09/11/18 14:04), Sergey Senozhatsky wrote:
> > > for (;;) {
> > > set_current_state(TASK_UNINTERRUPTIBLE);
> >
> > I think that set_current_state() also executes memory barrier. Just
> > because it accesses task state.
> >
> > > - if (!waiter.task)
> > > + if (!READ_ONCE(waiter.task))
> > > break;
> > > if (!timeout)
> > > break;
>
> This READ_ONCE(waiter.task) looks interesting. Maybe could be moved
> to a loop condition
>
> while (!READ_ONCE(waiter.task)) {
> ...
> }
No, it must be after set_current_state(). See that same comment.
next prev parent reply other threads:[~2018-09-11 11:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-11 1:48 [PATCHv3 0/6] tty: Hold write ldisc sem in tty_reopen() Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 1/6] tty: Drop tty->count on tty_reopen() failure Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 2/6] tty/ldsem: Update waiter->task before waking up reader Dmitry Safonov
2018-09-11 5:04 ` Sergey Senozhatsky
2018-09-11 5:41 ` Sergey Senozhatsky
2018-09-11 11:04 ` Kirill Tkhai
2018-09-11 11:44 ` Peter Zijlstra [this message]
2018-09-11 11:43 ` Peter Zijlstra
2018-09-11 11:40 ` Peter Zijlstra
2018-09-11 12:48 ` Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 3/6] tty: Hold tty_ldisc_lock() during tty_reopen() Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 4/6] tty/lockdep: Add ldisc_sem asserts Dmitry Safonov
2018-09-11 11:59 ` Peter Zijlstra
2018-09-11 12:01 ` Peter Zijlstra
2018-09-11 12:53 ` Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 5/6] tty: Simplify tty->count math in tty_reopen() Dmitry Safonov
2018-09-11 1:48 ` [PATCHv3 6/6] tty/ldsem: Decrement wait_readers on timeouted down_read() Dmitry Safonov
2018-09-11 12:02 ` Peter Zijlstra
2018-09-11 13:01 ` Dmitry Safonov
2018-09-11 13:33 ` Dmitry Safonov
2018-09-11 13:50 ` Peter Zijlstra
2018-09-11 15:04 ` Dmitry Safonov
2018-09-11 12:16 ` [PATCHv3 0/6] tty: Hold write ldisc sem in tty_reopen() Mark Rutland
2018-09-11 12:42 ` Dmitry Safonov
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