From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Barry Song <21cnbao@gmail.com>
Cc: linux-omap@vger.kernel.org, yongsheng.liu@csr.com,
linaro-dev <linaro-dev@lists.linaro.org>,
peiyu.li@csr.com, DL-SHA-WorkGroupLinux <workgroup.linux@csr.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: Is Pandaboard cpuhotplug working stably?
Date: Wed, 21 Dec 2011 10:07:06 +0000 [thread overview]
Message-ID: <20111221100706.GC3354@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAGsJ_4w0iVXC6qmDzmkuOb=ZN=Q0bF7EAFkxeYR_d7-vo+8bqQ@mail.gmail.com>
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.
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WARNING: multiple messages have this Message-ID (diff)
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: Is Pandaboard cpuhotplug working stably?
Date: Wed, 21 Dec 2011 10:07:06 +0000 [thread overview]
Message-ID: <20111221100706.GC3354@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAGsJ_4w0iVXC6qmDzmkuOb=ZN=Q0bF7EAFkxeYR_d7-vo+8bqQ@mail.gmail.com>
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.
next prev parent reply other threads:[~2011-12-21 10:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 9:23 Is Pandaboard cpuhotplug working stably? Barry Song
2011-12-21 9:23 ` Barry Song
2011-12-21 9:46 ` Russell King - ARM Linux
2011-12-21 9:46 ` Russell King - ARM Linux
2011-12-21 9:59 ` Barry Song
2011-12-21 9:59 ` Barry Song
2011-12-21 10:07 ` Russell King - ARM Linux [this message]
2011-12-21 10:07 ` Russell King - ARM Linux
2011-12-22 8:49 ` Shilimkar, Santosh
2011-12-22 8:49 ` Shilimkar, Santosh
2011-12-22 10:24 ` Russell King - ARM Linux
2011-12-22 10:24 ` Russell King - ARM Linux
2011-12-22 10:27 ` Shilimkar, Santosh
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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