From: paulmck@linux•vnet.ibm.com (Paul E. McKenney)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] opp: convert dev_warn() to dev_dbg() for duplicate OPPs
Date: Tue, 25 Nov 2014 08:25:22 -0800 [thread overview]
Message-ID: <20141125162522.GD5050@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAKohpo=dDTAV=B0CvCqD1H-QGuQ+i2w5Lfr3egpWzrvRYVNWmw@mail.gmail.com>
On Tue, Nov 25, 2014 at 04:07:35PM +0530, Viresh Kumar wrote:
> On 24 November 2014 at 21:44, Paul E. McKenney
> <paulmck@linux•vnet.ibm.com> wrote:
> > As Rafael says, if opp is reachable by RCU readers, you cannot just
> > immediately kfree() it. Immediately kfree()ing it like this -will-
> > cause your RCU readers to see freed memory, which, as you noted, can
> > cause crashes.
>
> In order to reply you at some level, I tried going through RCU documentation
> today before replying anymore. And yes I understood this part.
>
> > Except that srcu_notifier_call_chain() involves SRCU readers. So,
> > unless I am confused, you instead need something like this:
> >
> > static void kfree_opp_rcu(struct rcu_head *rhp)
> > {
> > struct device_opp *opp = container_of(rhp, struct device_opp, opp_list);
> >
> > kfree(opp);
> > }
> >
> > Then replace the above kfree() by:
> >
> > call_srcu(&opp->rcu, kfree_opp_rcu);
>
> Correct. But you missed the srcu which should be the first argument here :)
Indeed I did! ;-)
> > This will require adding the following to struct device_opp:
> >
> > struct rcu_head rcu;
>
> We were freeing struct dev_pm_opp, and so I believe you
> wanted me to add it there? Its already there.
Fair enough!
> > All that said, I do not claim to understand the OPP code, so please take
> > the above suggested changes with a grain of salt. And if you let me know
> > where I am confused, I should be able to offer better suggestions.
>
> Thanks for your suggestions. I have sent the patch to list and cc'd you on
> the relevant ones. Would be great if you can review the rcu part there.
Done!
Thanx, Paul
next prev parent reply other threads:[~2014-11-25 16:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 8:08 [PATCH] opp: convert dev_warn() to dev_dbg() for duplicate OPPs Viresh Kumar
2014-11-17 19:32 ` Stefan Wahren
2014-11-17 23:39 ` Rafael J. Wysocki
2014-11-18 3:08 ` Viresh Kumar
2014-11-18 20:51 ` Rafael J. Wysocki
2014-11-19 7:46 ` Viresh Kumar
2014-11-21 15:58 ` Rafael J. Wysocki
2014-11-24 10:40 ` Viresh Kumar
2014-11-24 15:09 ` Rafael J. Wysocki
2014-11-24 16:14 ` Paul E. McKenney
2014-11-25 1:27 ` Rafael J. Wysocki
2014-11-25 10:37 ` Viresh Kumar
2014-11-25 16:25 ` Paul E. McKenney [this message]
2014-11-25 6:32 ` Viresh Kumar
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