linux-kernel - Re: [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during cpu up/down

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Message-ID: <alpine.DEB.2.11.1507141743150.18576@nanos>
Date:	Tue, 14 Jul 2015 17:44:42 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Peter Anvin <hpa@...or.com>, xiao jin <jin.xiao@...el.com>,
	Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
	xen-devel <xen-devel@...ts.xenproject.org>
Subject: Re: [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during
 cpu up/down

On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
> > Prevent allocation and freeing of interrupt descriptors accross cpu
> > hotplug.
> 
> 
> This breaks Xen guests that allocate interrupt descriptors in .cpu_up().

And where exactly does XEN allocate those descriptors?
 
> Any chance this locking can be moved into arch code?

No.

> (The patch doesn't appear to have any side effects for the down path since Xen
> guests deallocate descriptors in __cpu_die()).
 
Exact place please.

Thanks,

	tglx
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