linux-kernel - Re: [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user

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Date:	Fri, 06 Feb 2015 22:53:34 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	kvm@...r.kernel.org, borntraeger@...ibm.com,
	linux-kernel@...r.kernel.org, mtosatti@...hat.com,
	mingo@...nel.orgm, ak@...ux.intel.com, oleg@...hat.com,
	masami.hiramatsu.pt@...achi.com, paulmck@...ux.vnet.ibm.com,
	lcapitulino@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user_enter/exit

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On 02/06/2015 06:15 PM, Frederic Weisbecker wrote:

> Just a few things then:
> 
> 1) In this case rename context_tracking_user_enter/exit() to 
> context_tracking_enter() and context_tracking_exit(), since it's
> not anymore about user only but about any generic context.
> 
> 2) We have the "WARN_ON_ONCE(!current->mm);" condition that is a
> debug check specific to userspace transitions because kernel
> threads aren't expected to resume to userspace. Can we also expect
> that we never switch to/from guest from a kernel thread? AFAICS
> this happens from an ioctl (thus user task) in x86 for kvm. But I
> only know this case.
> 
> 3) You might want to update a few comments that assume we only deal
> with userspace transitions.
> 
> 4) trace_user_enter/exit() should stay user-transitions specific.

Paul, would you like me to send follow-up patches with the cleanups
suggested by Frederic, or would you prefer me to send a new series
with the cleanups integrated?

Frederic, I will also add the cleanup you suggested for patch 4/5.

- -- 
All rights reversed
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