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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Andrew Morton <akpm@linux-foundation.org>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
        Tang Chen <tangchen@cn.fujitsu.com>, Vlastimil Babka <vbabka@suse.cz>,
        David Rientjes <rientjes@google.com>,
        Fabian Frederick <fabf@skynet.be>,
        Zhang Zhen <zhenzhang.zhang@huawei.com>,
        Vladimir Davydov <vdavydov@parallels.com>,
        Wang Nan <wangnan0@huawei.com>, linux-kernel@vger.kernel.org,
        devel@linuxdriverproject.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/3] driver core: export lock_device_hotplug/unlock_device_hotplug
Date: Thu, 12 Feb 2015 05:04:28 +0100
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On Wednesday, February 11, 2015 12:39:47 PM Andrew Morton wrote:
> On Wed, 11 Feb 2015 16:44:20 +0100 Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> 
> > add_memory() is supposed to be run with device_hotplug_lock grabbed, otherwise
> > it can race with e.g. device_online(). Allow external modules (hv_balloon for
> > now) to lock device hotplug.
> > 
> > ...
> >
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -55,11 +55,13 @@ void lock_device_hotplug(void)
> >  {
> >  	mutex_lock(&device_hotplug_lock);
> >  }
> > +EXPORT_SYMBOL_GPL(lock_device_hotplug);
> >  
> >  void unlock_device_hotplug(void)
> >  {
> >  	mutex_unlock(&device_hotplug_lock);
> >  }
> > +EXPORT_SYMBOL_GPL(unlock_device_hotplug);
> >  
> >  int lock_device_hotplug_sysfs(void)
> >  {
> 
> It's kinda crazy that lock_device_hotplug_sysfs() didn't get any
> documentation.  I suggest adding this while you're in there:
> 
> 
> --- a/drivers/base/core.c~a
> +++ a/drivers/base/core.c
> @@ -61,6 +61,9 @@ void unlock_device_hotplug(void)
>  	mutex_unlock(&device_hotplug_lock);
>  }
>  
> +/*
> + * "git show 5e33bc4165f3ed" for details
> + */
>  int lock_device_hotplug_sysfs(void)
>  {
>  	if (mutex_trylock(&device_hotplug_lock))
> 
> which is a bit lazy but whatev.
> 
> I'll assume that Greg (or Rafael?) will be processing this patchset.

Well, I would do that if I saw it (my address in the CC has been deprecated
for several months now).

Vitaly, can you please resend with a CC to a valid address of mine, please?

Rafael