From: Roland Dreier <rdreier@cisco.com>
To: "Moore\, Eric" <Eric.Moore@lsi.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: HELP: Is writeq an atomic operation??
Date: Fri, 02 May 2008 15:46:20 -0700 [thread overview]
Message-ID: <ada63tw494z.fsf@cisco.com> (raw)
In-Reply-To: <0631C836DBF79F42B5A60C8C8D4E822901047B2F@NAMAIL2.ad.lsil.com> (Eric Moore's message of "Fri, 2 May 2008 16:40:40 -0600")
> Is a 64bit write to MMIO registers an atomic operation when using the
> writeq API?
>
> My concern is when I send 64bit data via writeq, will it be sent out as
> two 32 bit writes? If so, is it possible that another CPU be sending
> the data at the same time. Meaning can I write the 1st 32bit data from
> CPU-A, meanwhile CPU-B is writing his 32bit data at the same time, and
> CPU-A didn't complete the full 64bit in one shot. If this could occur,
> is there an API that I can use to make sure the entire data sent in one
> atomic operation?
I don't have an authoritative answer, but I can say that I coded
drivers/infiniband/hw/mthca and .../mlx4 assuming that writeq() is
atomic in the sense that you say, and no one has reported any problems.
But I'm sure no one has stressed the drivers on 64-bit mips or anything
unusual like that.
- R.
next prev parent reply other threads:[~2008-05-02 22:46 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-02 22:40 HELP: Is writeq an atomic operation?? Moore, Eric
2008-05-02 22:46 ` Roland Dreier [this message]
2008-05-03 0:42 ` H. Peter Anvin
2008-05-03 14:35 ` Alan Cox
2008-05-03 17:40 ` H. Peter Anvin
2008-05-03 22:37 ` Benjamin Herrenschmidt
2008-05-04 17:01 ` Roland Dreier
2008-05-02 22:50 ` Andi Kleen
2008-05-02 23:03 ` Moore, Eric
2008-05-02 23:13 ` Andi Kleen
2008-05-02 23:04 ` Roland Dreier
2008-05-02 23:20 ` Moore, Eric
2008-05-03 0:10 ` Roland Dreier
2008-05-02 23:12 ` Jesse Barnes
2008-05-03 0:41 ` H. Peter Anvin
[not found] <0631C836DBF79F42B5A60C8C8D4E822901047B1D@NAMAIL2.ad.lsil.com>
2008-05-02 22:32 ` David Miller
2008-05-02 22:43 ` Roland Dreier
2008-05-02 22:49 ` David Miller
2008-05-02 22:49 ` Moore, Eric
2008-05-02 22:53 ` Roland Dreier
2008-05-02 23:13 ` Moore, Eric
2008-05-02 23:21 ` Roland Dreier
2008-05-02 23:31 ` Moore, Eric
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=ada63tw494z.fsf@cisco.com \
--to=rdreier@cisco.com \
--cc=Eric.Moore@lsi.com \
--cc=linux-kernel@vger.kernel.org \
/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