From: Ryan Arnold <rsa@us.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc64-dev <linuxppc64-dev@lists.linuxppc.org>,
Paul Mackerras <paulus@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] interrupt driven hvc_console as vio device
Date: Wed, 25 Aug 2004 00:12:53 -0500 [thread overview]
Message-ID: <1093410773.3402.111.camel@localhost> (raw)
In-Reply-To: <20040824214950.5d9043a3.akpm@osdl.org>
On Tue, 2004-08-24 at 23:49, Andrew Morton wrote:
> > + spin_lock_irqsave(&hp->lock, flags);
> > + retval = N_OUTBUF - hp->n_outbuf;
> > + spin_unlock_irqrestore(&hp->lock, flags);
> The new locking in these functions doesn't really do anything, apart from
> adding memory barriers. If that's what you really want, I suggest you
> simply add (commented) memory barriers.
Since chars_in_buffer() can be called from the tty write task and the
n_outbuf value is changed from the hvc_console task I didn't want there
to be any confusion as to the real value of the variable when
chars_in_buffer() was reading it. Is this the proper scenario for a
memory barrier?
Ryan S. Arnold
IBM Linux Technology Center
next prev parent reply other threads:[~2004-08-25 17:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-25 0:48 [PATCH] interrupt driven hvc_console as vio device Ryan Arnold
2004-08-25 4:46 ` Andrew Morton
2004-08-25 5:09 ` Ryan Arnold
2004-08-25 4:49 ` Andrew Morton
2004-08-25 5:12 ` Ryan Arnold [this message]
2004-08-25 4:59 ` Paul Mackerras
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