From: Segher Boessenkool <segher@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
Cc: netdev@vger.kernel.org, jgarzik@pobox.com, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] gianfar: Add I/O barriers when touching buffer descriptor ownership.
Date: Wed, 2 May 2007 20:05:43 +0200 [thread overview]
Message-ID: <4334c860f893dbc537a51999cea25532@kernel.crashing.org> (raw)
In-Reply-To: <4638B673.4090504@freescale.com>
>> AFAICS you need stronger barriers though; {w,r,}mb(),
>> to prevent _any_ reordering of those memory accesses,
>> not just the compiler-generated ones.
>
> My impression was that the eieio used by iobarrier would be sufficient
> for that, as we're not trying to synchronize between accesses to
> different types of memory. Is sync really required here?
For accesses to main system memory, eieio only orders
writes, not reads, so iobarrier_r() doesn't do what
you want; and iobarrier_w() isn't meant to be used for
main memory access ordering either.
Also, it is better to not use powerpc-specific interfaces
in a device driver if you don't have a strong reason to.
Segher
next prev parent reply other threads:[~2007-05-02 18:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-01 16:55 [PATCH] gianfar: Add I/O barriers when touching buffer descriptor ownership Scott Wood
2007-05-02 0:54 ` Segher Boessenkool
2007-05-02 16:04 ` Scott Wood
2007-05-02 18:05 ` Segher Boessenkool [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-05-16 20:06 Scott Wood
2007-05-18 0:45 ` Jeff Garzik
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4334c860f893dbc537a51999cea25532@kernel.crashing.org \
--to=segher@kernel.crashing.org \
--cc=jgarzik@pobox.com \
--cc=linuxppc-dev@ozlabs.org \
--cc=netdev@vger.kernel.org \
--cc=scottwood@freescale.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).