linux-kernel - Re: [xen] double fault: 0000 [#1] PREEMPT SMP DEBUG

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Date:	Thu, 10 Oct 2013 03:23:45 +0100 (IST)
From:	Dave Airlie <airlied@...ux.ie>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	xen-devel@...ts.xenproject.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [xen] double fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC


> I think David Arlie also needs a quiet talking to about how to use the
> device model:
> 
> int drm_sysfs_device_add(struct drm_minor *minor)
> {
>         minor->kdev.release = drm_sysfs_device_release;
> ...
>         err = device_register(&minor->kdev);
> }
> 
> static void drm_sysfs_device_release(struct device *dev)
> {
>         memset(dev, 0, sizeof(struct device));
>         return;
> }
> 
> Since when has that been acceptable in a release function?

Well the commit that added it had a reason that seems to cover some other 
device model abuses, so maybe someone who actually understands the device 
model (all 2 people) can review usage.

Dave.

commit 77d26dc9b9805f322f5a1f6e559b18ad66205bd9
Author: Ma Ling <ling.ma@...el.com>
Date:   Thu Apr 16 17:51:25 2009 +0800

    drm: clean dirty memory after device release
    
    In current code we register/unregister connector object by
    drm_sysfs_connector_add/remove function.
    
    However under some cases, we need to dynamically register or 
unregister device
    multiple times, so we have to go through register -> unregister 
->register
    routine.
    
    Because after device_unregister function our memory is dirty, we need 
to do
    clean operation in order to re-register the device, otherwise the 
system
    will crash.  The patch intends to clean device after device release.
    
    Signed-off-by: Ma Ling <ling.ma@...el.com>
    Signed-off-by: Dave Airlie <airlied@...hat.com>


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