linux-kernel - Re: [PATCH 24/32] Task fork and exit for rdtgroup

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Date:	Wed, 13 Jul 2016 15:14:31 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Fenghua Yu <fenghua.yu@...el.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Tony Luck <tony.luck@...el.com>, Tejun Heo <tj@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	David Carrillo-Cisneros <davidcc@...gle.com>,
	Ravi V Shankar <ravi.v.shankar@...el.com>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	Sai Prakhya <sai.praneeth.prakhya@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH 24/32] Task fork and exit for rdtgroup

On Tue, 12 Jul 2016, Fenghua Yu wrote:
> +void rdtgroup_fork(struct task_struct *child)
> +{
> +	INIT_LIST_HEAD(&child->rg_list);
> +	child->rdtgroup = NULL;
> +}
> +
> +void rdtgroup_post_fork(struct task_struct *child)
> +{
> +	if (!use_rdtgroup_tasks)
> +		return;
> +
> +	spin_lock_irq(&rdtgroup_task_lock);
> +	if (list_empty(&child->rg_list)) {

Why would the list be non empty after a fork?

> +		struct rdtgroup *rdtgrp = current->rdtgroup;
> +
> +		list_add_tail(&child->rg_list, &rdtgrp->pset.tasks);
> +		child->rdtgroup = rdtgrp;
> +		atomic_inc(&rdtgrp->pset.refcount);
> +	}
> +	spin_unlock_irq(&rdtgroup_task_lock);
> +}
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 9e6e135..04346b6 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -59,6 +59,7 @@
>  #include <asm/unistd.h>
>  #include <asm/pgtable.h>
>  #include <asm/mmu_context.h>
> +#include <asm/intel_rdt.h>
>  
>  static void __unhash_process(struct task_struct *p, bool group_dead)
>  {
> @@ -757,6 +758,7 @@ void do_exit(long code)
>  	perf_event_exit_task(tsk);
>  
>  	cgroup_exit(tsk);
> +	rdtgroup_exit(tsk);

-ENOSUCHFUNCTION

Please provide the implementations first and then hook it up not the other way
round.

Thanks,

	tglx