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[Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblo
From: |
Paul Brook |
Subject: |
[Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes |
Date: |
Wed, 5 May 2010 15:10:48 +0100 |
User-agent: |
KMail/1.13.3 (Linux/2.6.33-2-amd64; KDE/4.4.3; x86_64; ; ) |
> On 05/05/2010 08:34 AM, Paul Brook wrote:
> >> I really dislike the idea of adding another function for this. Can you
> >> explain why you need this functionality for virtio-console and why this
> >> functionality isn't needed for everything else?
> >
> > This functionality should (in principle) be used by all serial port
> > implementations.
> >
> > Physical serial ports are sufficiently crufty and low-performance that
> > noone actually uses them nowadays. I expect that the only significant
> > real-world use is for serial consoles, which never send enough data to
> > care that writes stall the whole machine.
>
> We don't implement control flow in the character driver layer today.
> Different backends use different policies. Some drop data (like pty)
> while other block (like tcp).
Really? I thought data was only dropped when no client was connected, and that
there was a user visible option to control this. Either way, I agree that
this should be done consistently.
> This patch adds optional control flow in a pretty crufty way to *some*
> backends but not all. This just adds a bunch of complexity that will
> certainly introduce bugs.
I admit I've only really looked at the device emulation side of the interface,
not the chardev backend implementation.
Paul
- [Qemu-devel] [PATCH v7 1/6] virtio-console: Factor out common init between console and generic ports, (continued)
- [Qemu-devel] [PATCH v7 1/6] virtio-console: Factor out common init between console and generic ports, Amit Shah, 2010/05/04
- [Qemu-devel] [PATCH v7 2/6] char: Add a QemuChrHandlers struct to initialise chardev handlers, Amit Shah, 2010/05/04
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Amit Shah, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Paul Brook, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes,
Paul Brook <=
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Gerd Hoffmann, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Gerd Hoffmann, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Gerd Hoffmann, 2010/05/06
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Gerd Hoffmann, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 3/6] char: Let writers know how much data was written in case of errors, Anthony Liguori, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 3/6] char: Let writers know how much data was written in case of errors, Amit Shah, 2010/05/05
- [Qemu-devel] Re: [PATCH v7 3/6] char: Let writers know how much data was written in case of errors, Anthony Liguori, 2010/05/05