Re: [PATCH]broadcast IPI race condition on CPU hotplug

[Andi Kleen]

On Wed, Apr 27, 2005 at 09:11:59AM +0800, Li Shaohua wrote:
> On Tue, 2005-04-26 at 21:21, Andi Kleen wrote:
> > On Tue, Apr 26, 2005 at 10:20:44AM +0800, Li Shaohua wrote:
> > > Hi,
> > > After a CPU is booted but before it's officially up (set online map, and
> > > enable interrupt), the CPU possibly will receive a broadcast IPI. After
> > > it's up, it will handle the stale interrupt soon and maybe cause oops if
> > > it's a smp-call-function-interrupt. This is quite possible in CPU
> > > hotplug case, but nearly can't occur at boot time. Below patch replaces
> > > broadcast IPI with send_ipi_mask just like the cluster mode.
> > 
> > No way we are making this common operation much slower just
> > to fix an obscure race at boot time. PLease come up with a fix
> > that only impacts the boot process.
> We can't prevent a CPU to receive a broadcast interrupt. Ack the
> interrupt and mark the cpu online can't be atomic operation, so the CPU
> either receives unexpected interrupt or loses interrupt.

Cant you just check at the end of the CPU bootup if the CPU
got such an APIC interrupt and ack it then? 

-Andi
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