[PATCH] OMAP2 PM: do RCU locking for opp_get_voltage()

[PATCH] OMAP2 PM: do RCU locking for opp_get_voltage()

[Arnout Vandecappelle (Essensium/Mind)]

From: "Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be>

According to the documentation of opp_get_voltage(), it must be called
with rcu_read_lock() held.  The OMAP2 power manager doesn't do this.
The locking error is caught by PROVE_RCU.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
---
Please CC me, I'm not on the list.

I was very surprised by this error, because this is the only user of
opp_get_voltage().

Regards,
Arnout
---
 arch/arm/mach-omap2/pm.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-omap2/pm.c b/arch/arm/mach-omap2/pm.c
index 00bff46..bce2bdc 100644
--- a/arch/arm/mach-omap2/pm.c
+++ b/arch/arm/mach-omap2/pm.c
@@ -174,14 +174,17 @@ static int __init omap2_set_init_voltage(char *vdd_name, char *clk_name,
 	freq = clk->rate;
 	clk_put(clk);
 
+	rcu_read_lock();
 	opp = opp_find_freq_ceil(dev, &freq);
 	if (IS_ERR(opp)) {
 		pr_err("%s: unable to find boot up OPP for vdd_%s\n",
 			__func__, vdd_name);
+		rcu_read_unlock();
 		goto exit;
 	}
 
 	bootup_volt = opp_get_voltage(opp);
+	rcu_read_unlock();
 	if (!bootup_volt) {
 		pr_err("%s: unable to find voltage corresponding "
 			"to the bootup OPP for vdd_%s\n", __func__, vdd_name);
-- 
1.7.8.3

Re: [PATCH] OMAP2 PM: do RCU locking for opp_get_voltage()

[Kevin Hilman]

"Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be> writes:

> From: "Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be>
>
> According to the documentation of opp_get_voltage(), it must be called
> with rcu_read_lock() held.  The OMAP2 power manager doesn't do this.
> The locking error is caught by PROVE_RCU.
>
> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

Thanks for the patch, I've got a patch from Neil Brown queued for this
already:

       http://marc.info/?l=linux-omap&m=132608991812586&w=2

Kevin

> ---
> Please CC me, I'm not on the list.
>
> I was very surprised by this error, because this is the only user of
> opp_get_voltage().
>
> Regards,
> Arnout
> ---
>  arch/arm/mach-omap2/pm.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/pm.c b/arch/arm/mach-omap2/pm.c
> index 00bff46..bce2bdc 100644
> --- a/arch/arm/mach-omap2/pm.c
> +++ b/arch/arm/mach-omap2/pm.c
> @@ -174,14 +174,17 @@ static int __init omap2_set_init_voltage(char *vdd_name, char *clk_name,
>  	freq = clk->rate;
>  	clk_put(clk);
>  
> +	rcu_read_lock();
>  	opp = opp_find_freq_ceil(dev, &freq);
>  	if (IS_ERR(opp)) {
>  		pr_err("%s: unable to find boot up OPP for vdd_%s\n",
>  			__func__, vdd_name);
> +		rcu_read_unlock();
>  		goto exit;
>  	}
>  
>  	bootup_volt = opp_get_voltage(opp);
> +	rcu_read_unlock();
>  	if (!bootup_volt) {
>  		pr_err("%s: unable to find voltage corresponding "
>  			"to the bootup OPP for vdd_%s\n", __func__, vdd_name);