From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Nathan Lynch <ntl@pobox.com>
Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH] fix gettimeofday vs. update_gtod race
Date: Tue, 22 Aug 2006 07:43:10 +1000 [thread overview]
Message-ID: <1156196590.21752.52.camel@localhost.localdomain> (raw)
In-Reply-To: <20060821212555.GC9828@localdomain>
On Mon, 2006-08-21 at 16:25 -0500, Nathan Lynch wrote:
> Nathan Lynch wrote:
> > Benjamin Herrenschmidt wrote:
> > > On Wed, 2006-08-16 at 19:18 -0500, Nathan Lynch wrote:
> > >
> > > > No? I didn't find anything about mftb having synchronizing
> > > > behavior. How should we ensure that temp_varp is assigned before
> > > > reading the timebase?
> > >
> > > I sync an isync would be enough.
> >
> > I see, thanks.
>
> Actually, after checking Book 2 and discussing with some other folks
> I'm not so sure -- isync "may complete before storage accesses
> associated with instructions preceding the isync instruction have been
> performed."
Of sure, I was thinking about isync preventing mftb from being executed
and we can have a proper data dependency. Anyway, that's not necessary,
I've looked at the code and we no longer need to pass the tb value in
(it's historical). Thus we can just move the mftb in the protected area
and maybe with a twi/isync pair make sure we got the gtod pointer before
we do the mftb
Ben.
prev parent reply other threads:[~2006-08-21 21:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-11 20:41 [PATCH] fix gettimeofday vs. update_gtod race Nathan Lynch
2006-08-16 23:48 ` Benjamin Herrenschmidt
2006-08-17 0:18 ` Nathan Lynch
2006-08-17 0:27 ` Benjamin Herrenschmidt
2006-08-17 20:47 ` Nathan Lynch
2006-08-21 21:25 ` Nathan Lynch
2006-08-21 21:43 ` Benjamin Herrenschmidt [this message]
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=1156196590.21752.52.camel@localhost.localdomain \
--to=benh@kernel.crashing.org \
--cc=anton@samba.org \
--cc=linuxppc-dev@ozlabs.org \
--cc=ntl@pobox.com \
--cc=paulus@samba.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;
as well as URLs for NNTP newsgroup(s).