linux-kernel - Re: [patch] pm_qos update fixing mmotm 2010-05-11 -dies in pm_qos_update

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Message-Id: <201005170021.25427.rjw@sisk.pl>
Date:	Mon, 17 May 2010 00:21:25 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	markgross@...gnar.org
Cc:	Valdis.Kletnieks@...eu, mgross@...ux.intel.com,
	akpm@...ux-foundation.org, davem@...emloft.net,
	linux-kernel@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	netdev@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [patch] pm_qos update fixing mmotm 2010-05-11 -dies in pm_qos_update_request()

On Saturday 15 May 2010, mgross wrote:
> On Sat, May 15, 2010 at 09:38:47PM +0200, Rafael J. Wysocki wrote:
> > On Saturday 15 May 2010, mgross wrote:
> > > I apologize for the goofy email address.  
> > > 
> > > The following is a fix for the crash reported by Valdis.
> > > 
> > > The problem was that the original pm_qos silently fails when a request
> > > update is passed to a parameter that has not been added to the list
> > > yet.  It seems that the e1000e is doing this.  This update restores this
> > > behavior.
> > > 
> > > I need to think about how to better handle such abuse, but for now this
> > > restores the original behavior.
> > 
> > Can you please post a signed-off incremental patch against
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6.git for-llinus
> > 
> > that contains your original PM QOS update?
> 
> No problem:
>
> Signed-off-by: markgross <markgross@...gnar.org>

Thanks!  Do you want to use this address for the sign-off or the Intel one?

Rafael

 
> From 487b8dcaeb66d3c226d4c06c1bd99689f93024be Mon Sep 17 00:00:00 2001
> From: mgross <mgross@...oss-desktop.(none)>
> Date: Sat, 15 May 2010 14:30:15 -0700
> Subject: [PATCH] Gard against pm_qos users calling API before registering a proper
>  request.
> 
> This update handles a use case where pm_qos update requests need to
> silently fail if the update is being sent to a handle that is null.
> 
> The problem was that the original pm_qos silently fails when a request
> update is passed to a parameter that has not been added to the list yet.
> This update restores that behavior.
> 
> Signed-off-by: markgross <markgross@...gnar.org>
> 
> ---
>  kernel/pm_qos_params.c |   26 ++++++++++++++------------
>  1 files changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
> index a1aea04..f42d3f7 100644
> --- a/kernel/pm_qos_params.c
> +++ b/kernel/pm_qos_params.c
> @@ -252,19 +252,21 @@ void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
>  	int pending_update = 0;
>  	s32 temp;
>  
> -	spin_lock_irqsave(&pm_qos_lock, flags);
> -	if (new_value == PM_QOS_DEFAULT_VALUE)
> -		temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
> -	else
> -		temp = new_value;
> -
> -	if (temp != pm_qos_req->value) {
> -		pending_update = 1;
> -		pm_qos_req->value = temp;
> +	if (pm_qos_req) { /*guard against callers passing in null */
> +		spin_lock_irqsave(&pm_qos_lock, flags);
> +		if (new_value == PM_QOS_DEFAULT_VALUE)
> +			temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
> +		else
> +			temp = new_value;
> +
> +		if (temp != pm_qos_req->value) {
> +			pending_update = 1;
> +			pm_qos_req->value = temp;
> +		}
> +		spin_unlock_irqrestore(&pm_qos_lock, flags);
> +		if (pending_update)
> +			update_target(pm_qos_req->pm_qos_class);
>  	}
> -	spin_unlock_irqrestore(&pm_qos_lock, flags);
> -	if (pending_update)
> -		update_target(pm_qos_req->pm_qos_class);
>  }
>  EXPORT_SYMBOL_GPL(pm_qos_update_request);
>  
> 

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