Re: [PATCH RFC v2 3/7] cgroup: Add interface to allow drivers to lookup process cgroup membership

From: Matt Roper <matthew.d.roper@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tejun Heo <tj@kernel.org>,
	cgroups@vger.kernel.org, intel-gfx@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH RFC v2 3/7] cgroup: Add interface to allow drivers to lookup process cgroup membership
Date: Thu, 1 Feb 2018 13:25:26 -0800	[thread overview]
Message-ID: <20180201212526.GI31510@mdroper-desk.amr.corp.intel.com> (raw)
In-Reply-To: <151751817231.28099.3778306702580372716@mail.alporthouse.com>

On Thu, Feb 01, 2018 at 08:49:32PM +0000, Chris Wilson wrote:
> Quoting Matt Roper (2018-02-01 19:53:11)
...
> > +struct cgroup *
> > +cgroup_for_driver_process(struct pid *pid)
> > +{
> > +       struct task_struct *task = pid_task(pid, PIDTYPE_PID);
> > +
> > +       mutex_lock(&cgroup_mutex);
> > +       spin_lock_irq(&css_set_lock);
> > +       task_cgroup_from_root(task, &cgrp_dfl_root);
> > +       spin_unlock_irq(&css_set_lock);
> > +       mutex_unlock(&cgroup_mutex);
> 
> Gut feeling says use task = get_pid_task(); if (!task) return NULL and
> put_task_struct(task); for safety.
> 
> Shouldn't there be a return here?

Woops, looks like I mis-squashed some of my fixes for this patch in to
patch #4 instead.  But yeah, get_pid_task() is better in general.

Matt

> > +}
> -Chris
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-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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