Re: Warning in irq_work_queue_on()

From: Peter Zijlstra
Date: Wed Sep 02 2015 - 18:24:38 EST


On Wed, Sep 02, 2015 at 11:50:22PM +0200, Frederic Weisbecker wrote:
> > > [ 875.703227] [<ffffffff810c2d74>] tick_nohz_full_kick_cpu+0x44/0x50
>
> It happens in nohz full, but I'm not sure the guilty is nohz full.
>
> The problem here is that wake_up_nohz_cpu() selects a CPU that is offline.

wake_up_nohz_cpu() doesn't do any such thing. Where does the selection
logic live?

> But this shouldn't happen. Either it selects a CPU that is in the domain tree,
> and I suspect offline CPUs aren't supposed to be there, or it selects the current
> CPU. And if the CPU is offlined, it shouldn't be running some kthread...

Do no assume things like that.. always check with the active mask.
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