Re: [PATCH v3 06/10] hwmon: (fam15h_power) Add compute unit accumulated power

[Huang Rui <ray.huang@amd.com>]

On Fri, Oct 30, 2015 at 06:33:42PM +0800, kbuild test robot wrote:
> Hi Huang,
> 
> [auto build test WARNING on hwmon/hwmon-next -- if it's inappropriate base, please suggest rules for selecting the more suitable base]
> 
> url:    https://github.com/0day-ci/linux/commits/Huang-Rui/hwmon-fam15h_power-Introduce-an-accumulated-power-reporting-algorithm/20151030-181426
> config: x86_64-randconfig-x012-10300134 (attached as .config)
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
> http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from arch/x86/include/asm/cpumask.h:4:0,
>                     from arch/x86/include/asm/msr.h:10,
>                     from arch/x86/include/asm/processor.h:20,
>                     from arch/x86/include/asm/atomic.h:6,
>                     from include/linux/atomic.h:4,
>                     from include/linux/debug_locks.h:5,
>                     from include/linux/lockdep.h:23,
>                     from include/linux/spinlock_types.h:18,
>                     from include/linux/mutex.h:15,
>                     from include/linux/kernfs.h:13,
>                     from include/linux/sysfs.h:15,
>                     from include/linux/kobject.h:21,
>                     from include/linux/device.h:17,
>                     from include/linux/hwmon-sysfs.h:23,
>                     from drivers/hwmon/fam15h_power.c:23:
>    drivers/hwmon/fam15h_power.c: In function 'fam15h_power_probe':
> >> include/linux/cpumask.h:24:29: warning: 'res_mask' may be used uninitialized in this function [-Wmaybe-uninitialized]
>     #define cpumask_bits(maskp) ((maskp)->bits)
>                                 ^
>    drivers/hwmon/fam15h_power.c:145:32: note: 'res_mask' was declared here
>      cpumask_var_t mask, tmp_mask, res_mask;
>                                    ^

Thank you to capture it! That's because my machine doesn't enable
CONFIG_CPUMASK_OFFSTACK. So I didn't find this issue before.  :)

It needs to allocate res_mask like below:

---
diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
index 71c9e6c..499776b 100644
--- a/drivers/hwmon/fam15h_power.c
+++ b/drivers/hwmon/fam15h_power.c
@@ -172,6 +172,10 @@ static int read_registers(struct fam15h_power_data *data)
 	if (!ret)
 		return -ENOMEM;
 
+	ret = zalloc_cpumask_var(&res_mask, GFP_KERNEL);
+	if (!ret)
+		return -ENOMEM;
+
 	get_online_cpus();
 	this_cpu = get_cpu();
 
@@ -199,6 +203,7 @@ static int read_registers(struct fam15h_power_data *data)
 	put_cpu();
 	put_online_cpus();
 
+	free_cpumask_var(res_mask);
 	free_cpumask_var(tmp_mask);
 	free_cpumask_var(mask);
 
---

Thanks,
Rui