From: Jiri Slaby <jslaby@suse.cz>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jack Stone <jwjstone@fastmail.fm>, Mac <kmac@poczta.fm>,
linux-kernel@vger.kernel.org, linux-ppp@vger.kernel.org,
Greg Kroah-Hartman <gregkh@suse.de>,
Jiri Slaby <jirislaby@gmail.com>
Subject: Re: 'scheduling while atomic' during ppp connection on 2.6.37.1 and 2.6.38
Date: Mon, 21 Mar 2011 10:15:41 +0100 [thread overview]
Message-ID: <4D87173D.50906@suse.cz> (raw)
In-Reply-To: <20110320215826.79cadfe2@lxorguk.ukuu.org.uk>
On 03/20/2011 10:58 PM, Alan Cox wrote:
>> + spin_lock_irqsave(&dc->spin_mutex, flags);
>> if (port->port.count)
>> room = kfifo_avail(&port->fifo_ul);
>> - mutex_unlock(&port->tty_sem);
>> + spin_unlock_irqrestore(&dc->spin_mutex, flags);
>
> dc->spin_mutex does not protect port->port.count.
Neither port->tty_sem did.
Anyway is the test needed at all? I.e. could
tty->ops->write/chars_in_buffer/ntty_write_room be called with
port->port.count == 0 at all?
And the lock should not as well be needed. Kfifo assures atomicity where
there is only one reader and one writer which should be the case here.
Unless tty->ops->write can be called in parallel. And it should not,
that's what's tty->atomic_write_lock for.
thanks,
--
js
suse labs
next prev parent reply other threads:[~2011-03-21 9:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-19 22:06 'scheduling while atomic' during ppp connection on 2.6.37.1 and 2.6.38 Mac
2011-03-20 18:42 ` Jack Stone
2011-03-20 21:52 ` Jiri Slaby
2011-03-20 23:09 ` Jack Stone
2011-03-20 21:58 ` Alan Cox
2011-03-20 23:05 ` Jack Stone
2011-03-21 11:27 ` Alan Cox
2011-03-21 17:40 ` Jack Stone
2011-03-21 9:15 ` Jiri Slaby [this message]
2011-03-21 11:02 ` Alan Cox
2011-03-31 20:53 ` Jiri Slaby
2011-03-31 21:39 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2011-03-19 21:56 Mac
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