From: Ian Campbell <Ian.Campbell@citrix.com>
To: "karim.allah.ahmed@gmail.com" <karim.allah.ahmed@gmail.com>
Cc: xen-devel@lists.xenproject.org, Thomas Leonard <talex5@gmail.com>,
Julien Grall <julien.grall@linaro.org>,
Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [PATCH 6/7] mini-os: Added rmb to xenbus code
Date: Fri, 6 Jun 2014 15:15:42 +0100 [thread overview]
Message-ID: <1402064142.1313.62.camel@kazak.uk.xensource.com> (raw)
In-Reply-To: <CAOTdubu-AQmqFdn5L3hh9q1RkrDvoJdxwtWW_T5QB9T-CVDBkg@mail.gmail.com>
On Fri, 2014-06-06 at 05:59 +0100, karim.allah.ahmed@gmail.com wrote:
> In any case, by looking at the patch it seems like rmb was required to
> make sure that the reply message is visible to the current processor
> when this thread wakes up and starts reading it.
Can we assume (or arrange) that schedule() gives us this guarantee? Do
we want to?
I don't think the current schedule() common code guarantees this, and
obviously the x86 arch code doesn't care. Someone should decide...
>
> I'll have a look at the other patches and put some comments there as well.
>
> Regards.
>
> On Thu, Jun 5, 2014 at 6:45 PM, Thomas Leonard <talex5@gmail.com> wrote:
> > Hi Karim,
> >
> > Do you remember what this rmb call is for? It's from your commit here:
> >
> > https://github.com/KarimAllah/xen/commit/61e8edeb9eabdf575f6f8e7720d977f07d907579#diff-dd67cee31c935093d2c65298a1d5b267R455
> >
> > https://github.com/KarimAllah/xen/blob/61e8edeb9eabdf575f6f8e7720d977f07d907579/extras/mini-os/xenbus/xenbus.c#L455
> >
> > Also, if you have any information to add to the other commits, that
> > would be very useful:
> >
> > https://github.com/talex5/xen/commits/sent-Jun-04
> >
> >
> >
> > On 5 June 2014 14:55, Julien Grall <julien.grall@linaro.org> wrote:
> >> Hi Thomas,
> >>
> >> Thank you for the patch.
> >>
> >> On 06/04/2014 05:06 PM, Thomas Leonard wrote:
> >>> From: Karim Raslan <karim.allah.ahmed@gmail.com>
> >>>
> >>> Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
> >>> [talex5@gmail.com: separated from big ARM commit]
> >>> Signed-off-by: Thomas Leonard <talex5@gmail.com>
> >>> ---
> >>> extras/mini-os/xenbus/xenbus.c | 1 +
> >>> 1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/extras/mini-os/xenbus/xenbus.c b/extras/mini-os/xenbus/xenbus.c
> >>> index d995020..8a99ee2 100644
> >>> --- a/extras/mini-os/xenbus/xenbus.c
> >>> +++ b/extras/mini-os/xenbus/xenbus.c
> >>> @@ -450,6 +450,7 @@ xenbus_msg_reply(int type,
> >>> remove_waiter(w, req_info[id].waitq);
> >>> wake(current);
> >>>
> >>> + rmb();
> >>
> >> Could you explain in the commit message why this rmb is necessary?
> >>
> >> Regards,
> >>
> >> --
> >> Julien Grall
> >
> >
> >
> > --
> > Dr Thomas Leonard http://0install.net/
> > GPG: 9242 9807 C985 3C07 44A6 8B9A AE07 8280 59A5 3CC1
> > GPG: DA98 25AE CAD0 8975 7CDA BD8E 0713 3F96 CA74 D8BA
>
>
>
next prev parent reply other threads:[~2014-06-06 14:15 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-02 17:49 [PATCH 0/4] mini-os: initial ARM support Thomas Leonard
2014-06-02 17:49 ` [PATCH 1/4] mini-os: Fixed shutdown thread Thomas Leonard
2014-06-03 0:51 ` Samuel Thibault
2014-06-03 9:01 ` Andrew Cooper
2014-06-02 17:49 ` [PATCH 2/4] mini-os: Tidied up code Thomas Leonard
2014-06-03 0:57 ` Samuel Thibault
2014-06-02 17:49 ` [PATCH 3/4] mini-os: Initial commit to port minios to ARM Thomas Leonard
2014-06-03 9:12 ` Julien Grall
2014-06-04 16:06 ` [PATCH 0/7] mini-os: Preparing for ARM support Thomas Leonard
2014-06-04 16:06 ` [PATCH 1/7] mini-os: Fixed shutdown thread Thomas Leonard
2014-06-04 16:06 ` [PATCH 2/7] mini-os: Tidied up code Thomas Leonard
2014-06-04 16:22 ` Andrew Cooper
2014-06-05 10:24 ` Anil Madhavapeddy
2014-06-04 16:06 ` [PATCH 3/7] mini-os: Moved events code under arch Thomas Leonard
2014-06-04 16:23 ` Julien Grall
2014-06-06 13:54 ` Ian Campbell
2014-06-06 13:57 ` Ian Campbell
2014-06-04 16:06 ` [PATCH 4/7] mini-os: Switched initial C entry point to arch_init Thomas Leonard
2014-06-06 14:05 ` Ian Campbell
2014-06-04 16:06 ` [PATCH 5/7] mini-os: Moved arch-specific xenbus code under arch Thomas Leonard
2014-06-05 14:00 ` Julien Grall
2014-06-06 14:07 ` Ian Campbell
2014-06-04 16:06 ` [PATCH 6/7] mini-os: Added rmb to xenbus code Thomas Leonard
2014-06-05 13:55 ` Julien Grall
2014-06-05 17:45 ` Thomas Leonard
2014-06-06 4:59 ` karim.allah.ahmed
2014-06-06 14:15 ` Ian Campbell [this message]
2014-06-06 15:10 ` Samuel Thibault
2014-06-06 16:40 ` Ian Campbell
2014-06-09 13:56 ` Thomas Leonard
2014-06-09 14:04 ` Thomas Leonard
2014-06-04 16:06 ` [PATCH 7/7] mini-os: Moved force_evtchn_callback to header Thomas Leonard
2014-06-06 14:17 ` Ian Campbell
2014-06-09 11:54 ` Thomas Leonard
2014-06-04 16:12 ` [PATCH 0/7] mini-os: Preparing for ARM support Andrew Cooper
2014-06-02 17:49 ` [PATCH 4/4] mini-os: Added FDT support on ARM Thomas Leonard
2014-06-06 13:51 ` Ian Campbell
2014-06-05 14:36 ` [PATCH 0/4] mini-os: initial ARM support Oleksandr Tyshchenko
2014-06-05 14:57 ` Samuel Thibault
2014-06-05 17:20 ` Oleksandr Tyshchenko
2014-06-05 17:31 ` Thomas Leonard
2014-06-05 18:07 ` Oleksandr Tyshchenko
2014-06-05 18:12 ` Thomas Leonard
2014-06-05 18:21 ` Oleksandr Tyshchenko
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