From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: paulmck@linux.vnet.ibm.com
Cc: Nishanth Menon <nm@ti.com>,
linux-pm <linux-pm@lists.linux-foundation.org>,
lkml <linux-kernel@vger.kernel.org>,
linux-arm <linux-arm-kernel@lists.infradead.org>,
linux-omap <linux-omap@vger.kernel.org>
Subject: Re: [PATCH v4] power: introduce library for device-specific OPPs
Date: Sat, 25 Sep 2010 22:55:20 +0200 [thread overview]
Message-ID: <201009252255.20933.rjw@sisk.pl> (raw)
In-Reply-To: <20100924193742.GJ2375@linux.vnet.ibm.com>
On Friday, September 24, 2010, Paul E. McKenney wrote:
> On Fri, Sep 24, 2010 at 07:50:40AM -0500, Nishanth Menon wrote:
...
>
> Looks like a good start!!! Some questions and suggestions about RCU
> usage interspersed below.
...
> > + * Locking: RCU reader.
> > + */
> > +int opp_get_opp_count(struct device *dev)
> > +{
> > + struct device_opp *dev_opp;
> > + struct opp *temp_opp;
> > + int count = 0;
> > +
> > + dev_opp = find_device_opp(dev);
> > + if (IS_ERR(dev_opp))
> > + return PTR_ERR(dev_opp);
> > +
> > + rcu_read_lock();
> > + list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
> > + if (temp_opp->available)
> > + count++;
> > + }
> > + rcu_read_unlock();
>
> This one is OK as well. You are returning a count, so if all of the
> counted structures are freed at this point, no problem. The count was
> valid when it was accumulated, and the fact that it might now be obsolete
> is (usually) not a problem.
However, it looks like it should run rcu_read_lock() before calling
find_device_opp(dev), shouldn't it?
Rafael
WARNING: multiple messages have this Message-ID (diff)
From: rjw@sisk.pl (Rafael J. Wysocki)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4] power: introduce library for device-specific OPPs
Date: Sat, 25 Sep 2010 22:55:20 +0200 [thread overview]
Message-ID: <201009252255.20933.rjw@sisk.pl> (raw)
In-Reply-To: <20100924193742.GJ2375@linux.vnet.ibm.com>
On Friday, September 24, 2010, Paul E. McKenney wrote:
> On Fri, Sep 24, 2010 at 07:50:40AM -0500, Nishanth Menon wrote:
...
>
> Looks like a good start!!! Some questions and suggestions about RCU
> usage interspersed below.
...
> > + * Locking: RCU reader.
> > + */
> > +int opp_get_opp_count(struct device *dev)
> > +{
> > + struct device_opp *dev_opp;
> > + struct opp *temp_opp;
> > + int count = 0;
> > +
> > + dev_opp = find_device_opp(dev);
> > + if (IS_ERR(dev_opp))
> > + return PTR_ERR(dev_opp);
> > +
> > + rcu_read_lock();
> > + list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
> > + if (temp_opp->available)
> > + count++;
> > + }
> > + rcu_read_unlock();
>
> This one is OK as well. You are returning a count, so if all of the
> counted structures are freed at this point, no problem. The count was
> valid when it was accumulated, and the fact that it might now be obsolete
> is (usually) not a problem.
However, it looks like it should run rcu_read_lock() before calling
find_device_opp(dev), shouldn't it?
Rafael
next prev parent reply other threads:[~2010-09-25 20:55 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <[PATCH v3] power: introduce library for device-specific OPPs>
2010-09-24 12:50 ` [PATCH v4] power: introduce library for device-specific OPPs Nishanth Menon
2010-09-24 12:50 ` Nishanth Menon
2010-09-24 19:37 ` Paul E. McKenney
2010-09-24 19:37 ` Paul E. McKenney
2010-09-24 21:26 ` Nishanth Menon
2010-09-24 21:26 ` Nishanth Menon
2010-09-24 21:40 ` Paul E. McKenney
2010-09-24 21:40 ` Paul E. McKenney
2010-09-24 21:40 ` Paul E. McKenney
2010-09-27 14:29 ` Nishanth Menon
2010-09-27 14:29 ` Nishanth Menon
2010-09-27 14:29 ` Nishanth Menon
2010-09-24 21:26 ` Nishanth Menon
2010-09-25 20:55 ` Rafael J. Wysocki [this message]
2010-09-25 20:55 ` Rafael J. Wysocki
2010-09-26 0:56 ` Paul E. McKenney
2010-09-26 0:56 ` Paul E. McKenney
2010-09-27 14:25 ` Nishanth Menon
2010-09-27 14:25 ` Nishanth Menon
2010-09-27 14:25 ` Nishanth Menon
2010-09-27 19:53 ` Rafael J. Wysocki
2010-09-27 19:53 ` Rafael J. Wysocki
2010-09-27 19:53 ` Rafael J. Wysocki
2010-09-27 14:25 ` Nishanth Menon
2010-09-26 0:56 ` Paul E. McKenney
2010-09-25 20:55 ` Rafael J. Wysocki
2010-09-24 19:37 ` Paul E. McKenney
2010-09-24 19:37 ` Paul E. McKenney
2010-09-24 12:50 ` Nishanth Menon
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