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Subject[patch V2 09/13] cpufreq/ia64: Replace racy task affinity logic
The get() and target() callbacks must run on the affected cpu. This is
achieved by temporarily setting the affinity of the calling thread to the
requested CPU and reset it to the original affinity afterwards.

That's racy vs. concurrent affinity settings for that thread resulting in
code executing on the wrong CPU and overwriting the new affinity setting.

Replace it by work_on_cpu(). All call pathes which invoke the callbacks are
already protected against CPU hotplug.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-pm@vger.kernel.org
---

V2: Fixup kbuild-robot complaints

drivers/cpufreq/ia64-acpi-cpufreq.c | 92 +++++++++++++++---------------------
1 file changed, 39 insertions(+), 53 deletions(-)

Index: b/drivers/cpufreq/ia64-acpi-cpufreq.c
===================================================================
--- a/drivers/cpufreq/ia64-acpi-cpufreq.c
+++ b/drivers/cpufreq/ia64-acpi-cpufreq.c
@@ -34,6 +34,11 @@ struct cpufreq_acpi_io {
unsigned int resume;
};

+struct cpufreq_acpi_req {
+ unsigned int cpu;
+ unsigned int state;
+};
+
static struct cpufreq_acpi_io *acpi_io_data[NR_CPUS];

static struct cpufreq_driver acpi_cpufreq_driver;
@@ -83,8 +88,7 @@ processor_get_pstate (
static unsigned
extract_clock (
struct cpufreq_acpi_io *data,
- unsigned value,
- unsigned int cpu)
+ unsigned value)
{
unsigned long i;

@@ -98,60 +102,43 @@ extract_clock (
}


-static unsigned int
+static long
processor_get_freq (
- struct cpufreq_acpi_io *data,
- unsigned int cpu)
+ void *arg)
{
- int ret = 0;
- u32 value = 0;
- cpumask_t saved_mask;
- unsigned long clock_freq;
+ struct cpufreq_acpi_req *req = arg;
+ unsigned int cpu = req->cpu;
+ struct cpufreq_acpi_io *data = acpi_io_data[cpu];
+ u32 value;
+ int ret;

pr_debug("processor_get_freq\n");
-
- saved_mask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, cpumask_of(cpu));
if (smp_processor_id() != cpu)
- goto migrate_end;
+ return -EAGAIN;

/* processor_get_pstate gets the instantaneous frequency */
ret = processor_get_pstate(&value);
-
if (ret) {
- set_cpus_allowed_ptr(current, &saved_mask);
pr_warn("get performance failed with error %d\n", ret);
- ret = 0;
- goto migrate_end;
+ return ret;
}
- clock_freq = extract_clock(data, value, cpu);
- ret = (clock_freq*1000);
-
-migrate_end:
- set_cpus_allowed_ptr(current, &saved_mask);
- return ret;
+ return 1000 * extract_clock(data, value);
}


-static int
+static long
processor_set_freq (
- struct cpufreq_acpi_io *data,
- struct cpufreq_policy *policy,
- int state)
+ void *arg)
{
- int ret = 0;
- u32 value = 0;
- cpumask_t saved_mask;
- int retval;
+ struct cpufreq_acpi_req *req = arg;
+ unsigned int cpu = req->cpu;
+ struct cpufreq_acpi_io *data = acpi_io_data[cpu];
+ int ret, state = req->state;
+ u32 value;

pr_debug("processor_set_freq\n");
-
- saved_mask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, cpumask_of(policy->cpu));
- if (smp_processor_id() != policy->cpu) {
- retval = -EAGAIN;
- goto migrate_end;
- }
+ if (smp_processor_id() != cpu)
+ return -EAGAIN;

if (state == data->acpi_data.state) {
if (unlikely(data->resume)) {
@@ -159,8 +146,7 @@ processor_set_freq (
data->resume = 0;
} else {
pr_debug("Already at target state (P%d)\n", state);
- retval = 0;
- goto migrate_end;
+ return 0;
}
}

@@ -171,7 +157,6 @@ processor_set_freq (
* First we write the target state's 'control' value to the
* control_register.
*/
-
value = (u32) data->acpi_data.states[state].control;

pr_debug("Transitioning to state: 0x%08x\n", value);
@@ -179,17 +164,11 @@ processor_set_freq (
ret = processor_set_pstate(value);
if (ret) {
pr_warn("Transition failed with error %d\n", ret);
- retval = -ENODEV;
- goto migrate_end;
+ return -ENODEV;
}

data->acpi_data.state = state;
-
- retval = 0;
-
-migrate_end:
- set_cpus_allowed_ptr(current, &saved_mask);
- return (retval);
+ return 0;
}


@@ -197,11 +176,13 @@ static unsigned int
acpi_cpufreq_get (
unsigned int cpu)
{
- struct cpufreq_acpi_io *data = acpi_io_data[cpu];
+ struct cpufreq_acpi_req req;
+ long ret;

- pr_debug("acpi_cpufreq_get\n");
+ req.cpu = cpu;
+ ret = work_on_cpu(cpu, processor_get_freq, &req);

- return processor_get_freq(data, cpu);
+ return ret > 0 ? (unsigned int) ret : 0;
}


@@ -210,7 +191,12 @@ acpi_cpufreq_target (
struct cpufreq_policy *policy,
unsigned int index)
{
- return processor_set_freq(acpi_io_data[policy->cpu], policy, index);
+ struct cpufreq_acpi_req req;
+
+ req.cpu = policy->cpu;
+ req.state = index;
+
+ return work_on_cpu(req.cpu, processor_set_freq, &req);
}

static int
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