From mboxrd@z Thu Jan  1 00:00:00 1970
From: Amit Shah <amit.shah@redhat.com>
Subject: Re: [PATCH 7/7] virtio: console: Return -EPIPE if port on the host
	isn't connected
Date: Tue, 23 Mar 2010 16:39:57 +0530
Message-ID: <20100323110957.GB3080@amit-x200.redhat.com>
References: <1269334680-1369-4-git-send-email-amit.shah@redhat.com>
	<1269334680-1369-5-git-send-email-amit.shah@redhat.com>
	<1269334680-1369-6-git-send-email-amit.shah@redhat.com>
	<1269334680-1369-7-git-send-email-amit.shah@redhat.com>
	<1269334680-1369-8-git-send-email-amit.shah@redhat.com>
	<20100323090023.GD22774@redhat.com>
	<20100323091352.GI8675@amit-x200.redhat.com>
	<4BA89C1E.7090403@redhat.com>
	<20100323105220.GK8675@amit-x200.redhat.com>
	<4BA8A03C.8030002@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <virtualization-bounces@lists.linux-foundation.org>
Content-Disposition: inline
In-Reply-To: <4BA8A03C.8030002@redhat.com>
List-Unsubscribe: <https://lists.linux-foundation.org/mailman/listinfo/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=unsubscribe>
List-Archive: <http://lists.linux-foundation.org/pipermail/virtualization>
List-Post: <mailto:virtualization@lists.linux-foundation.org>
List-Help: <mailto:virtualization-request@lists.linux-foundation.org?subject=help>
List-Subscribe: <https://lists.linux-foundation.org/mailman/listinfo/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=subscribe>
Sender: virtualization-bounces@lists.linux-foundation.org
Errors-To: virtualization-bounces@lists.linux-foundation.org
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: virtualization@lists.linux-foundation.org, "Michael S. Tsirkin" <mst@redhat.com>
List-Id: virtualization@lists.linuxfoundation.org

On (Tue) Mar 23 2010 [12:04:28], Gerd Hoffmann wrote:
> On 03/23/10 11:52, Amit Shah wrote:
>
>>> With poll support done right (don't signal "writable" when not
>>> connected) this shouldn't be a issue.  Apps retrying over and over
>>> without waiting for the filehandle becoming writable are broken by
>>> design.
>>
>> Yeah; poll returns POLLOUT only when the host connection is open. This
>> is for apps that write() without consulting poll().
>
> Well, /me just remembers this also depends on the file mode.  Returning  
> -EAGAIN instantly is fine for non-blocking file handles.  For file  
> handles in blocking mode you would have to block here, waiting for the  
> host to connect.

Ah, right.

I didn't really look at blocking / non-blocking support in write()
because of the cpu_relax(), which will always block the app.

I'll add this.

		Amit