linux-kernel - Re: [PATCH] TTY: Fix loss of echoed characters (2nd follow-on PATCH attached)

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Date:	Mon, 8 Sep 2008 17:32:50 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Peterson <joe@...rush.com>
Cc:	alan@...rguk.ukuu.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] TTY: Fix loss of echoed characters (2nd follow-on PATCH
 attached)

On Mon, 08 Sep 2008 10:11:46 -0600
Joe Peterson <joe@...rush.com> wrote:

> +	spin_lock_irqsave(&tty->echo_lock, flags);
>  	lock_kernel();

Taking a spinlock outside lock_kernel() isn't good, and is quite unusual.

- It might be ab/ba deadlockable (I didn't check) (I trust you always
  test with lockdep enabled?)

- will make Ingo unhappy when he applies his "make lock_kernel use
  mutex_lock" patch (if it's still around).

- will probably give the -rt guys conniptions.


swapping the above two lines would presumably be an easy fix, but one
wonders whether we still need lock_kernel() in there once you've added
this lock.

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