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From: Alan <alan@lxorguk.ukuu.org.uk>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andrew Morton <akpm@osdl.org>,
	linux-kernel@vger.kernel.org, virtualization@lists.osdl.org,
	xen-devel@lists.xensource.com,
	Ian Pratt <ian.pratt@xensource.com>,
	Christian Limpach <Christian.Limpach@cl.cam.ac.uk>,
	Chris Wright <chrisw@sous-sol.org>
Subject: Re: [patch 16/20] XEN-paravirt: Add the Xen virtual console driver.
Date: Sun, 14 Jan 2007 00:37:52 +0000	[thread overview]
Message-ID: <20070114003752.27a5cac4@localhost.localdomain> (raw)
In-Reply-To: <20070113014648.767777869@goop.org>

> +#endif
> +		tty_insert_flip_char(xencons_tty, buf[i], 0);

Please use the defines like TTY_NORMAL not just 0. 

> +		if ((xencons_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
> +		    (xencons_tty->ldisc.write_wakeup != NULL))
> +			(xencons_tty->ldisc.write_wakeup)(xencons_tty);
> +	}

You are't allowed to derefence and call ldisc methods without
holding the lock. You can replace that chunk with a call to the helper
function tty_wakeup(tty). Small but real race condition otherwise as you
xencons_tty->ldisc may be changing as you call it.

> +static inline int __xencons_put_char(int ch)
> +{
> +	char _ch = (char)ch;
> +	if ((wp - wc) == wbuf_size)
> +		return 0;
> +	wbuf[WBUF_MASK(wp++)] = _ch;
> +	return 1;
> +}

A lot of very confusing sign stuff here - you turn an int into a char and
put it into a uchar array

> +	for (i = 0; i < count; i++)
> +		if (!__xencons_put_char(buf[i]))
> +			break;

The int coming from a uchar array

Don't think its wrong - just acutely weird and perhaps could be tidier

> +static void xencons_close(struct tty_struct *tty, struct file *filp)
> +{
> +	unsigned long flags;
> +
> +	mutex_lock(&tty_mutex);

It would be good in future if you could avoid using tty_mutex and use a
private lock. At the moment vt "borrows" it and there are a couple of
incestuous spots but the plan is to eventually fix them and make it
private to tty_io.


Andrew: No objection to this tty stuff being merged provided the bugs
noted above (not worried about the sign stuff) are fixed before it goes
on to Linus.

Alan

  reply	other threads:[~2007-01-14  0:27 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-13  1:45 [patch 00/20] XEN-paravirt: Xen guest implementation for paravirt_ops interface Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 01/20] XEN-paravirt: Fix typo in sync_constant_test_bit()s name Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 02/20] XEN-paravirt: Add a flag to allow the VGA console to be disabled Jeremy Fitzhardinge
2007-01-14  0:27   ` [Xen-devel] " Alan
2007-01-13  1:45 ` [patch 03/20] XEN-paravirt: paravirt: page-table accessors Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 04/20] XEN-paravirt: paravirt pagetable init Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 05/20] XEN-paravirt: paravirt: reserve fixmap slot Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 06/20] XEN-paravirt: remove pgd ctor Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 07/20] XEN-paravirt: paravirt shared kernel pmd flag Jeremy Fitzhardinge
2007-01-15  8:59   ` [Xen-devel] " Jan Beulich
2007-01-13  1:45 ` [patch 08/20] XEN-paravirt: paravirt pgd allocation alignment Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 09/20] XEN-paravirt: dont export paravirt_ops structure, do individual functions Jeremy Fitzhardinge
2007-01-14  0:57   ` Rusty Russell
2007-01-13  1:45 ` [patch 10/20] XEN-paravirt: mm lifetime hooks Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 11/20] XEN-paravirt: Add apply_to_page_range() which applies a function to a pte range Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 12/20] XEN-paravirt: Xen: Add nosegneg capability to the vsyscall page notes Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 13/20] XEN-paravirt: Xen: Add config options and disable unsupported config options Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 15/20] XEN-paravirt: Xen: core paravirt guest changes Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 16/20] XEN-paravirt: Add the Xen virtual console driver Jeremy Fitzhardinge
2007-01-14  0:37   ` Alan [this message]
2007-01-14  0:35     ` Jeremy Fitzhardinge
2007-01-15 13:03   ` Pavel Machek
2007-01-19  4:11     ` Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 17/20] XEN-paravirt: Add Xen grant table support Jeremy Fitzhardinge
2007-01-15 13:05   ` Pavel Machek
2007-01-19  4:07     ` Jeremy Fitzhardinge
2007-01-13  1:45 ` [patch 18/20] XEN-paravirt: Add Xen driver utility functions Jeremy Fitzhardinge
2007-01-14  7:41   ` Greg KH
2007-01-13  1:45 ` [patch 19/20] XEN-paravirt: Add the Xenbus sysfs and virtual device hotplug driver Jeremy Fitzhardinge
2007-01-15 13:18   ` Pavel Machek
2007-01-13  1:45 ` [patch 20/20] XEN-paravirt: Add Xen virtual block device driver Jeremy Fitzhardinge
2007-01-14  1:07   ` Arjan van de Ven
2007-01-14  7:43     ` Greg KH
2007-01-16  2:53     ` [Xen-devel] " Mark Williamson
2007-01-14 11:05   ` Jan Engelhardt
2007-01-14 11:24     ` Muli Ben-Yehuda
2007-01-14 11:35       ` Jan Engelhardt
2007-01-14 12:37     ` Keir Fraser

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