From: Timur Tabi <timur@freescale.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Scott Wood <scottwood@freescale.com>,
linuxppc-dev@ozlabs.org, brueckner@linux.vnet.ibm.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] hvc_console: returning 0 from put_chars is not an error
Date: Thu, 15 Oct 2009 13:55:03 -0500 [thread overview]
Message-ID: <4AD77007.2070706@freescale.com> (raw)
In-Reply-To: <200910152041.26646.borntraeger@de.ibm.com>
Christian Borntraeger wrote:
> Hmmm, if we are ok with having both options, we should let the hvc backend
> decide if it wants to drain or to discard.
>
> If we just busy loop, it actually does not matter how we let hvc_console react
> on 0, as long as we adopt all backends to use that interface consistent.
>
> On the other hand, backends might want to do special magic on congestion so I
> personally tend to let the backend loop instead of hvc_console. But I am really
> not sure.
The reason that we're asking for this change is that I have an hvc client driver that drops characters during heavy printk() output. hvc calls my driver, but the output buffer is still full, so the driver just returns 0.
If I add a spin-loop in the driver, then we don't need to change hvc, but now the driver is blocking during user-space print operations (via hvc_write and hvc_push).
--
Timur Tabi
Linux kernel developer at Freescale
next prev parent reply other threads:[~2009-10-15 18:55 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 [this message]
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
2009-10-16 18:03 ` Benjamin Herrenschmidt
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