From: Shawn Guo <shawnguo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
LAK <linux-arm-kernel@lists.infradead.org>,
Zhengyu Shen <zhengyu.shen@nxp.com>, Frank Li <frank.li@nxp.com>,
Sebastian Sewior <bigeasy@linutronix.de>
Subject: Re: ARM: imx: mmdc: Fix completely broken cpu hotplug code
Date: Thu, 22 Dec 2016 08:57:08 +0800 [thread overview]
Message-ID: <20161222005705.GA11972@dragon> (raw)
In-Reply-To: <alpine.DEB.2.20.1612211928430.3424@nanos>
On Wed, Dec 21, 2016 at 07:32:06PM +0100, Thomas Gleixner wrote:
> On Wed, 21 Dec 2016, Thomas Gleixner wrote:
> > The cpu hotplug support of this perf driver is broken in several ways:
> >
> > 1) It adds a instance before setting up the state.
> >
> > 2) The state for the instance is different from the state of the
> > callback. It's just a randomly chosen state.
> >
> > 3) The instance registration is not error checked so nobody noticed that
> > the call can never succeed.
> >
> > 4) The state for the multi install callbacks is chosen randomly and
> > overwrites existing state. This is now prevented by the core code so the
> > call is guaranteed to fail.
> >
> > 5) The error exit path in the init function leaves the instance registered
> > and then frees the memory which contains the enqueued hlist node.
> >
> > 6) The remove function is removing the state and not the instance.
> >
> > Fix it by:
> >
> > - Setting up the state before adding instances. Use a dynamically allocated
> > state for it.
> >
> > - Install instances after the state has been set up
> >
> > - Remove the instance in the error path before freeing memory
> >
> > - Remove instance not the state in the driver remove callback
> >
> > While at is use raw_cpu_processor_id(), because cpu_processor_id() cannot
> > be used in preemptible context, and set the driver data after successful
> > registration of the pmu.
> >
> > Fixes: e76bdfd7403a ("ARM: imx: Added perf functionality to mmdc driver")
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Zhengyu Shen <zhengyu.shen@nxp.com>
> > Cc: Frank Li <frank.li@nxp.com>
> > Cc: Shawn Guo <shawnguo@kernel.org>
Acked-by: Shawn Guo <shawnguo@kernel.org>
>
> Shawn,
>
> as I have the final hotplug notifier removal pending here, which will break
> also the compilation of this driver, I would prefer to merge that through
> my tree before the removal patches to avoid build breakage.
Okay, thanks for taking care of it.
Shawn
prev parent reply other threads:[~2016-12-22 0:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-21 18:21 ARM: imx: mmdc: Fix completely broken cpu hotplug code Thomas Gleixner
2016-12-21 18:32 ` Thomas Gleixner
2016-12-22 0:57 ` Shawn Guo [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161222005705.GA11972@dragon \
--to=shawnguo@kernel.org \
--cc=bigeasy@linutronix.de \
--cc=frank.li@nxp.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=zhengyu.shen@nxp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).