From: Scott Wood <scottwood@freescale•com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org,
Linux Kernel Mailing List <linux-kernel@vger•kernel.org>,
Christian Borntraeger <borntraeger@de•ibm.com>,
brueckner@linux•vnet.ibm.com, Timur Tabi <timur@freescale•com>,
Alan Cox <alan@lxorguk•ukuu.org.uk>
Subject: Re: [PATCH] hvc_console: returning 0 from put_chars is not an error
Date: Fri, 16 Oct 2009 10:33:30 -0500 [thread overview]
Message-ID: <20091016153330.GB11838@loki.buserror.net> (raw)
In-Reply-To: <1255668405.19032.13.camel@pasglop>
On Fri, Oct 16, 2009 at 03:46:45PM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2009-10-15 at 13:57 -0500, Scott Wood wrote:
> > I'd say the dropping approach is quite undesirable (significant
> > potential for output loss unless the buffer is huge), unless there's
> > simply no way to safely spin. Hopefully there are no such backends, but
> > if there are perhaps we can have them return some special code to
> > indicate that.
>
> Should never spin.
Why is a hypervisor console different than a serial port in this regard?
> Best is to keep a copy in the upper layer of the pending data and throttle
> (not accept further data from tty layer) until we have managed to flush
> out that "pending" buffer.
The data isn't coming from the tty layer -- we're talking about printk. How
do you throttle that without spinning?
I agree that it shouldn't spin when handling tty I/O.
-Scott
next prev parent reply other threads:[~2009-10-16 15:33 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-14 21:53 [PATCH] hvc_console: returning 0 from put_chars is not an error Timur Tabi
2009-10-15 11:05 ` Christian Borntraeger
2009-10-15 16:09 ` Scott Wood
2009-10-15 18:41 ` Christian Borntraeger
2009-10-15 18:55 ` Timur Tabi
2009-10-15 18:57 ` Scott Wood
2009-10-15 19:26 ` Christian Borntraeger
2009-10-15 19:32 ` Scott Wood
2009-10-16 8:49 ` Hendrik Brueckner
2009-10-17 23:17 ` Timur Tabi
2009-10-16 4:46 ` Benjamin Herrenschmidt
2009-10-16 15:33 ` Scott Wood [this message]
2009-10-16 18:03 ` Benjamin Herrenschmidt
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