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@xxxxxxxxxxxxxxxx> wrote: > > On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote: > >> 2011/12/21 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>: > >> > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
