From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: Is Pandaboard cpuhotplug working stably?
Date: Thu, 22 Dec 2011 10:24:54 +0000 [thread overview]
Message-ID: <20111222102454.GD3354@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAMQu2gy8mwJ-aKit0b4d7=4FkxeFakfnL-phy0eMOK81Oe=PCw@mail.gmail.com>
On Thu, Dec 22, 2011 at 02:19:23PM +0530, Shilimkar, Santosh wrote:
> + Peter Z
>
> On Wed, Dec 21, 2011 at 3:37 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> > On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
> >> 2011/12/21 Russell King - ARM Linux <linux@arm.linux.org.uk>:
> >> > cpu hotplug is basically totally buggered - the preconditions placed
> >> > upon the bringup code path are basically impossible to satisfy in any
> >> > shape or form at the moment.
> >> >
> >> > There's the requirement that the secondary CPU is marked online and
> >> > active before interrupts are enabled for the thread migration stuff
> >> > to behave correctly. ?However, this is incompatible with smp_call_function()
> >> > which will wait for online CPUs to respond to an IPI - which this one
> >> > won't because interrupts are disabled.
> >> >
> >> > I think there was some discussion about how to fix this but I don't
> >> > recall the details.
> >>
> >> thanks, Russell. then could i think this is an ARM-kernel-specific bug
> >> which exists on all ARM SMP chips for the moment?
> >> and that bug doesn't happen on x86:
> >
> > I don't think so. ?There's nothing ARM specific about it.
>
> There are few patches floating around for this issue. I posted one version
> long back [1] and then there was one more form Thomas G.
> The most recent is from one is from Peter Z [2] which is moving the
> fix for the cup online race to core code.
>
> Can you try Peter's patch with your test-case ?
>
> Regards,
> Santosh
>
> [1] https://lkml.org/lkml/2011/6/20/79
> [2] https://lkml.org/lkml/2011/12/15/255
[1] is already fixed - and is not the latest "problem" with this code.
Fixing the problem in [1] actually itself created the latest problem
with smp_call_function() which wasn't there before this change. Patch
[2] refers to this problem and proposes a fix for it.
next prev parent reply other threads:[~2011-12-22 10:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 9:23 Is Pandaboard cpuhotplug working stably? Barry Song
2011-12-21 9:46 ` Russell King - ARM Linux
2011-12-21 9:59 ` Barry Song
2011-12-21 10:07 ` Russell King - ARM Linux
2011-12-22 8:49 ` Shilimkar, Santosh
2011-12-22 10:24 ` Russell King - ARM Linux [this message]
2011-12-22 10:27 ` Shilimkar, Santosh
2011-12-27 4:49 ` Varun Wadekar
2012-01-03 17:21 ` Russell King - ARM Linux
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