linux-kernel - Re: Warning in irq_work_queue

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Message-ID: <20150902222427.GW19282@twins.programming.kicks-ass.net>
Date:	Thu, 3 Sep 2015 00:24:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Tejun Heo <tj@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Warning in irq_work_queue_on()

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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