linux-kernel - Re: [tip:sched/core] sched/cpuacct: Split usage accounting into user_usage and sys

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Message-ID: <20160406110803.GI2906@worktop>
Date:	Wed, 6 Apr 2016 13:08:03 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Anton Blanchard <anton@...ba.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	tglx@...utronix.de, efault@....de, htejun@...il.com,
	linux-kernel@...r.kernel.org, tj@...nel.org,
	torvalds@...ux-foundation.org, zhaolei@...fujitsu.com,
	yangds.fnst@...fujitsu.com, hpa@...or.com,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [tip:sched/core] sched/cpuacct: Split usage accounting into
 user_usage and sys_usage

On Wed, Apr 06, 2016 at 08:32:19PM +1000, Anton Blanchard wrote:
> Hi,
> 
> > > >  void cpuacct_charge(struct task_struct *tsk, u64 cputime)
> > > >  {
> > > >  	struct cpuacct *ca;
> > > > +	int index;
> > > > +
> > > > +	if (user_mode(task_pt_regs(tsk)))
> > > > +		index = CPUACCT_USAGE_USER;
> > > > +	else
> > > > +		index = CPUACCT_USAGE_SYSTEM;
> 
> This is oopsing because PowerPC task_pt_regs() returns NULL for
> kernel threads.

Ah, so sometihng like:

	struct pt_regs *regs = task_pt_regs();
	int index = CPUACCT_USAGE_SYSTEM;

	if (regs && user_mode(regs))
		index = CPUACCT_USAGE_USER;

should work, right?