From: Gerd Hoffmann <kraxel@redhat.com>
To: Paul Brook <paul@codesourcery.com>
Cc: Amit Shah <amit.shah@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu list <qemu-devel@nongnu.org>,
Juan Quintela <quintela@redhat.com>
Subject: [Qemu-devel] Re: [PATCH 0/8] (v2) chardev, virtio-console: flow control, error handling, fixes
Date: Mon, 12 Apr 2010 09:51:51 +0200 [thread overview]
Message-ID: <4BC2D117.30307@redhat.com> (raw)
In-Reply-To: <201004072358.53971.paul@codesourcery.com>
On 04/08/10 00:58, Paul Brook wrote:
>> Hello,
>>
>> This patchset introduces flow control to virtio-console and
>> chardev-based virtio serial ports. This series is based on the
>> previous series I sent on Mar 31st (00/17: v4: virtio-serial fixes,
>> new abi for port discovery)
>>
>> The qemu chardevs can now return -EAGAIN when a non-blocking remote
>> isn't ready to accept more data.
>>
>> Comments?
>
> This is a major change in semantics. Are you sure all users handle this
> correctly? My guess is that most of the devices don't.
I don't expect trouble here. EAGAIN is returned only for file handles
in non-blocking mode. I doubt existing users use non-blocking I/O as
this makes the current unix_write() code go busy-loop in case the
outgoing pipe is full.
> EAGAIN isn't really a useful response unless you have some way of notifying
> the device that it can send more data.
This is a valid point though.
cheers,
Gerd
next prev parent reply other threads:[~2010-04-12 7:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-07 21:02 [Qemu-devel] [PATCH 0/8] (v2) chardev, virtio-console: flow control, error handling, fixes Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 1/8] virtio-serial: throttling: check for throttled status before sending any data Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 2/8] virtio-serial: Unthrottle ports once they're closed Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 3/8] virtio-serial: Discard unconsumed data before sending port close event Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 4/8] virtio-serial: Bus info message for showing port's throttled status Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 5/8] char: Let writers know how much data was written in case of errors Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 6/8] char: unix: For files that are nonblocking, report -EAGAIN to calling functions Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 7/8] virtio-console: Factor out common init between console and generic ports Amit Shah
2010-04-07 21:02 ` [Qemu-devel] [PATCH 8/8] virtio-console: Throttle virtio-serial-bus if we can't consume any more guest data Amit Shah
2010-04-07 22:58 ` [Qemu-devel] Re: [PATCH 0/8] (v2) chardev, virtio-console: flow control, error handling, fixes Paul Brook
2010-04-12 7:51 ` Gerd Hoffmann [this message]
2010-04-12 11:42 ` Paul Brook
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