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Date: Tue, 24 Aug 2004 21:46:20 -0700
From: Andrew Morton <akpm@osdl.org>
To: Ryan Arnold <rsa@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, linuxppc64-dev@lists.linuxppc.org,
       paulus@samba.org, benh@kernel.crashing.org
Subject: Re: [PATCH] interrupt driven hvc_console as vio device
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Ryan Arnold <rsa@us.ibm.com> wrote:
>
>  static void hvc_close(struct tty_struct *tty, struct file * filp)
>   {
> ...
>  +		while (hp->n_outbuf) {
>  +			spin_unlock_irqrestore(&hp->lock, flags);
>  +			yield();
>  +			spin_lock_irqsave(&hp->lock, flags);
>  +		}

ick.

I suspect that if the caller of hvc_close() has realtime scheduling policy,
this locks up.  Unless it's waiting for interrupt activity.

Really, a real sleep/wakeup would be tons better.