From: Li Zhong <zhong@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com,
toshi.kani@hp.com
Subject: Re: [RFC PATCH v5 2/2] Use kernfs_break_active_protection() for device online store callbacks
Date: Fri, 09 May 2014 16:35:08 +0800 [thread overview]
Message-ID: <1399624508.2630.11.camel@ThinkPad-T5421.cn.ibm.com> (raw)
In-Reply-To: <1398137679.2805.28.camel@ThinkPad-T5421.cn.ibm.com>
viOn Tue, 2014-04-22 at 11:34 +0800, Li Zhong wrote:
> On Mon, 2014-04-21 at 18:46 -0400, Tejun Heo wrote:
> > Hello,
> >
> > On Mon, Apr 21, 2014 at 05:23:50PM +0800, Li Zhong wrote:
> >
> > Proper /** function comment would be nice.
>
> Ok, will try to write some in next version.
>
> >
> > > +struct kernfs_node *lock_device_hotplug_sysfs(struct device *dev,
> > > + struct device_attribute *attr)
> >
> > I can see why you did this but let's please not require the user of
> > this function to see how the thing is working internally. Let's
> > return int and keep track of (or look up again) the kernfs_node
> > internally.
>
> Ok, it also makes the prototype of lock and unlock look more consistent
> and comfortable.
When trying to do an new version of the patch, I find that if the device
is really removed, then we couldn't look up using the parent, and
attribute name again in unlock. So I guess maybe I could add one more
argument, e.g. kn_out,:q to track this kernfs node.
Code will be posted soon for your review.
Thanks, Zhong
>
> >
> > > {
> > ...
> > > + /*
> > > + * We assume device_hotplug_lock must be acquired before removing
> >
> > Is this assumption true? If so, can we add lockdep assertions in
> > places to verify and enforce this? If not, aren't we just feeling
> > good when the reality is broken?
>
> It seems not true ... I think there are devices that don't have the
> online/offline concept, we just need to add it, remove it, like ethernet
> cards.
>
> Maybe we could change the comments above, like:
> /* We assume device_hotplug_lock must be acquired before
> * removing devices, which have online/offline sysfs knob,
> * and some locks are needed to serialize the online/offline
> * callbacks and device removing. ...
> ?
>
> And we could add lockdep assertions in cpu and memory related code? e.g.
> remove_memory(), unregister_cpu()
>
> Currently, remove_memory() has comments for the function:
>
> * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
> * and online/offline operations before this call, as required by
> * try_offline_node().
> */
>
> maybe it could be removed with the lockdep assertion.
>
> > ...
> >
> > Function comment please.
>
> OK.
>
> Thanks, Zhong
>
> > > +void unlock_device_hotplug_sysfs(struct device *dev,
> > > + struct kernfs_node *kn)
> > > +{
> > > + unlock_device_hotplug();
> > > + kernfs_unbreak_active_protection(kn);
> > > + put_device(dev);
> > > + kernfs_put(kn);
> > > }
> >
> > Thanks.
> >
>
next prev parent reply other threads:[~2014-05-09 8:35 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-10 9:18 [RFC PATCH] Suppress a device hot remove related lockdep warning Li Zhong
2014-04-10 13:31 ` Tejun Heo
2014-04-11 4:10 ` [RFC PATCH v2] Use kernfs_break_active_protection() for device online store callbacks Li Zhong
2014-04-11 10:26 ` Tejun Heo
2014-04-14 7:47 ` [RFC PATCH v3] " Li Zhong
2014-04-14 20:13 ` Tejun Heo
2014-04-15 2:44 ` Li Zhong
2014-04-15 14:50 ` Tejun Heo
2014-04-16 1:41 ` Li Zhong
2014-04-16 15:17 ` Tejun Heo
2014-04-17 3:05 ` Li Zhong
2014-04-17 15:06 ` Tejun Heo
2014-04-17 6:50 ` [RFC PATCH v4] " Li Zhong
2014-04-17 15:17 ` Tejun Heo
2014-04-18 8:33 ` Li Zhong
2014-04-21 9:20 ` [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Li Zhong
2014-04-21 9:23 ` [RFC PATCH v5 2/2] Use kernfs_break_active_protection() for device online store callbacks Li Zhong
2014-04-21 22:46 ` Tejun Heo
2014-04-22 3:34 ` Li Zhong
2014-04-22 10:11 ` Rafael J. Wysocki
2014-04-23 1:50 ` Li Zhong
2014-04-23 10:54 ` Rafael J. Wysocki
2014-04-24 1:13 ` Li Zhong
2014-04-22 20:44 ` Tejun Heo
2014-04-22 22:21 ` Rafael J. Wysocki
2014-04-23 14:23 ` Tejun Heo
2014-04-23 16:12 ` Rafael J. Wysocki
2014-04-23 16:52 ` Tejun Heo
2014-04-24 8:59 ` Li Zhong
2014-04-24 10:02 ` Rafael J. Wysocki
2014-04-25 1:46 ` Li Zhong
2014-04-25 12:47 ` Rafael J. Wysocki
2014-04-28 1:49 ` Li Zhong
2014-04-23 5:03 ` Li Zhong
2014-04-23 10:58 ` Rafael J. Wysocki
2014-04-24 1:33 ` Li Zhong
2014-05-09 8:35 ` Li Zhong [this message]
2014-05-09 8:40 ` [RFC PATCH v6 1/2 ] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Li Zhong
2014-05-09 8:40 ` [RFC PATCH v6 2/2] Implement lock_device_hotplug_sysfs() by breaking active protection Li Zhong
2014-04-21 22:38 ` [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Tejun Heo
2014-04-22 2:29 ` Li Zhong
2014-04-22 20:40 ` Tejun Heo
2014-04-23 2:00 ` Li Zhong
2014-04-23 14:39 ` Tejun Heo
2014-04-24 8:37 ` Li Zhong
2014-04-24 14:32 ` Tejun Heo
2014-04-25 1:56 ` Li Zhong
2014-04-25 12:28 ` Tejun Heo
2014-04-28 0:51 ` Li Zhong
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