Re: [linux-pm] [PATCH v4] cpuidle: Add a sysfs entry to disable specific C state for debug purpose.

Andrew Morton
2012-03-16T22:23:32Z

On Wed, 14 Mar 2012 11:24:40 +0800
ShuoX Liu <shuox.liu@intel.com> wrote:

> From: ShuoX Liu <shuox.liu@intel.com>
>
> Some C states of new CPU might be not good. One reason is BIOS might configure
> them incorrectly. To help developers root cause it quickly, the patch adds a
> new sysfs entry, so developers could disable specific C state manually.
>
> In addition, C state might have much impact on performance tuning, as it takes
> much time to enter/exit C states, which might delay interrupt processing. With
> the new debug option, developers could check if a deep C state could impact
> performance and how much impact it could cause.
>
> ...
>
> +#define define_store_state_function(_name) \
> +static ssize_t store_state_##_name(struct cpuidle_state *state, \
> + const char *buf, size_t size) \
> +{ \
> + long value; \
> + if (!capable(CAP_SYS_ADMIN)) \
> + return -EPERM; \
> + kstrtol(buf, 0, &value); \
> + if (value) \
> + state->disable = 1; \
> + else \
> + state->disable = 0; \
> + return size; \
> +}

drivers/cpuidle/sysfs.c: In function 'store_state_disable':
drivers/cpuidle/sysfs.c:274: warning: ignoring return value of 'kstrtol', declared with attribute warn_unused_result

The check is there for a reason - the kernel shouldn't silently accept
random garbage inputs.

--- a/drivers/cpuidle/sysfs.c~cpuidle-add-a-sysfs-entry-to-disable-specific-c-state-for-debug-purpose-fix
+++ a/drivers/cpuidle/sysfs.c
@@ -238,9 +238,12 @@ static ssize_t store_state_##_name(struc
const char *buf, size_t size) \
{ \
long value; \
+ int err; \
if (!capable(CAP_SYS_ADMIN)) \
return -EPERM; \
- kstrtol(buf, 0, &value); \
+ err = kstrtol(buf, 0, &value); \
+ if (err) \
+ return err; \
if (value) \
state->disable = 1; \
else \
_