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Date: Tue, 7 Jul 2015 16:15:53 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
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,
"mnipxh@....com" <mnipxh@....com>,
"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH] acpi-cpufreq: replace per_cpu with driver_data of policy
On 07-07-15, 18:29, Pan Xinhui wrote:
>
> Now policy has field of driver_data, we can use it to get rid of per_cpu
> acpi_cpufreq_data.
Instead:
"Drivers can store their internal per-policy information in
policy->driver_data, lets use it."
> we have benefits after this replacing. 1) memory saving. 2) policy is
s/we/We
Also these points can be kept in separate lines :)
> shared by several cpus, per_cpu seems not correct. useing *driver_data*
using
> is more reasonable. 3) fix a memory leak in acpi_cpufreq_cpu_exit.
Not just that. You are also fixing NULL pointer dereferences if wrong
or uninitialized per-cpu data is used, because of a recent hotplug of
policy->cpu.
> as
> policy->cpu might change after cpu hotplug. So sometimes we cant't free
> *data*, use *driver_data* to fix it. 4) fix a zero return value of
> get_cur_freq_on_cpu. Only per_cpu(policy->cpu) is set to *data*, if we
> try to get cpufreq on other cpus, we get zero instead of correct values.
> Use *driver_data* to fix it.
>
> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
> ---
> drivers/cpufreq/acpi-cpufreq.c | 38 +++++++++++++++++++++++---------------
> 1 file changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 0136dfc..7f662dd 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -72,8 +72,6 @@ struct acpi_cpufreq_data {
> cpumask_var_t freqdomain_cpus;
> };
>
> -static DEFINE_PER_CPU(struct acpi_cpufreq_data *, acfreq_data);
> -
> /* acpi_perf_data is a pointer to percpu data. */
> static struct acpi_processor_performance __percpu *acpi_perf_data;
>
> @@ -144,7 +142,7 @@ static int _store_boost(int val)
>
> static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf)
> {
> - struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu);
> + struct acpi_cpufreq_data *data = policy->driver_data;
>
> return cpufreq_show_cpus(data->freqdomain_cpus, buf);
> }
> @@ -327,7 +325,8 @@ static void drv_write(struct drv_cmd *cmd)
> put_cpu();
> }
>
> -static u32 get_cur_val(const struct cpumask *mask)
> +static u32 get_cur_val(const struct cpumask *mask,
> + struct acpi_cpufreq_data *data)
Run checkpatch --strict to see some alignment warnings here..
> {
> struct acpi_processor_performance *perf;
> struct drv_cmd cmd;
> @@ -335,7 +334,7 @@ static u32 get_cur_val(const struct cpumask *mask)
> if (unlikely(cpumask_empty(mask)))
> return 0;
>
> - switch (per_cpu(acfreq_data, cpumask_first(mask))->cpu_feature) {
> + switch (data->cpu_feature) {
> case SYSTEM_INTEL_MSR_CAPABLE:
> cmd.type = SYSTEM_INTEL_MSR_CAPABLE;
> cmd.addr.msr.reg = MSR_IA32_PERF_CTL;
> @@ -346,7 +345,7 @@ static u32 get_cur_val(const struct cpumask *mask)
> break;
> case SYSTEM_IO_CAPABLE:
> cmd.type = SYSTEM_IO_CAPABLE;
> - perf = per_cpu(acfreq_data, cpumask_first(mask))->acpi_data;
> + perf = data->acpi_data;
> cmd.addr.io.port = perf->control_register.address;
> cmd.addr.io.bit_width = perf->control_register.bit_width;
> break;
> @@ -364,19 +363,26 @@ 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);
>
> + policy = cpufreq_cpu_get(cpu);
> + if (unlikely(!policy))
> + return 0;
> +
> + data = policy->driver_data;
Do
+ cpufreq_cpu_put(policy);
right here. No need of doing this towards the end.
> if (unlikely(data == NULL ||
> data->acpi_data == NULL || data->freq_table == NULL)) {
Maybe this if you like:
if (unlikely(! data || !data->acpi_data || !data->freq_table))
return 0;
> + cpufreq_cpu_put(policy);
> return 0;
> }
>
> cached_freq = data->freq_table[data->acpi_data->state].frequency;
And this freq_table thing gives you opportunity to write another
patch :)
policy already have: policy->freq_table :)
> - 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.
> @@ -385,6 +391,8 @@ static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
> data->resume = 1;
> }
>
> + cpufreq_cpu_put(policy);
> +
> pr_debug("cur freq = %u\n", freq);
>
> return freq;
> @@ -397,7 +405,7 @@ static unsigned int check_freqs(const struct cpumask *mask, unsigned int freq,
> unsigned int i;
>
> for (i = 0; i < 100; i++) {
> - cur_freq = extract_freq(get_cur_val(mask), data);
> + cur_freq = extract_freq(get_cur_val(mask, data), data);
> if (cur_freq == freq)
> return 1;
> udelay(10);
> @@ -408,7 +416,7 @@ static unsigned int check_freqs(const struct cpumask *mask, unsigned int freq,
> static int acpi_cpufreq_target(struct cpufreq_policy *policy,
> unsigned int index)
> {
> - struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu);
> + struct acpi_cpufreq_data *data = policy->driver_data;
> struct acpi_processor_performance *perf;
> struct drv_cmd cmd;
> unsigned int next_perf_state = 0; /* Index into perf table */
> @@ -673,7 +681,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
> }
>
> data->acpi_data = per_cpu_ptr(acpi_perf_data, cpu);
> - per_cpu(acfreq_data, cpu) = data;
> + policy->driver_data = data;
>
> if (cpu_has(c, X86_FEATURE_CONSTANT_TSC))
> acpi_cpufreq_driver.flags |= CPUFREQ_CONST_LOOPS;
> @@ -843,19 +851,19 @@ err_free_mask:
> free_cpumask_var(data->freqdomain_cpus);
> err_free:
> kfree(data);
> - per_cpu(acfreq_data, cpu) = NULL;
> + policy->driver_data = NULL;
>
> return result;
> }
>
> static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
> {
> - struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu);
> + struct acpi_cpufreq_data *data = policy->driver_data;
>
> pr_debug("acpi_cpufreq_cpu_exit\n");
>
> if (data) {
> - per_cpu(acfreq_data, policy->cpu) = NULL;
> + policy->driver_data = NULL;
> acpi_processor_unregister_performance(data->acpi_data,
> policy->cpu);
> free_cpumask_var(data->freqdomain_cpus);
> @@ -868,7 +876,7 @@ static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
>
> static int acpi_cpufreq_resume(struct cpufreq_policy *policy)
> {
> - struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu);
> + struct acpi_cpufreq_data *data = policy->driver_data;
>
> pr_debug("acpi_cpufreq_resume\n");
Rest looks fine.
--
viresh
--
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