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

From: Andrew Morton
Date: Mon Sep 08 2008 - 20:33:21 EST

On Mon, 08 Sep 2008 10:11:46 -0600
Joe Peterson <joe@xxxxxxxxxxx> 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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