linux-kernel - Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 7 Jul 2015 10:11:26 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Pan Xinhui <xinhuix.pan@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, rjw@...ysocki.net,
	viresh.kumar@...aro.org, "mnipxh@....com" <mnipxh@....com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver_data of
 policy

Hi Pan,

On Tue, Jul 07, 2015 at 08:43:26PM +0800, Pan Xinhui wrote:
> @@ -364,19 +363,24 @@ static u32 get_cur_val(const struct cpumask *mask)
>  
>  static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
>  {
> -	struct acpi_cpufreq_data *data = per_cpu(acfreq_data, cpu);
> +	struct acpi_cpufreq_data *data;
> +	struct cpufreq_policy *policy;
>  	unsigned int freq;
>  	unsigned int cached_freq;
>  
>  	pr_debug("get_cur_freq_on_cpu (%d)\n", cpu);
>  
> -	if (unlikely(data == NULL ||
> -		     data->acpi_data == NULL || data->freq_table == NULL)) {
> +	policy = cpufreq_cpu_get(cpu);
> +	if (unlikely(!policy))
> +		return 0;
> +
> +	data = policy->driver_data;
> +	cpufreq_cpu_put(policy);

If we put policy here can we guarantee that memory pointed to by data
stays valid? Shoudln't we issue cpufreq_cpu_put(policy) after we done
assessing the pointer?

> +	if (unlikely(!data || !data->acpi_data || !data->freq_table))
>  		return 0;
> -	}
>  
>  	cached_freq = data->freq_table[data->acpi_data->state].frequency;
> -	freq = extract_freq(get_cur_val(cpumask_of(cpu)), data);
> +	freq = extract_freq(get_cur_val(cpumask_of(cpu), data), data);
>  	if (freq != cached_freq) {
>  		/*
>  		 * The dreaded BIOS frequency change behind our back.

Thanks.

-- 
Dmitry
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/