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>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: linux-pm@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1704122231100.2548@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 39 insertions, 53 deletions

diff --git a/drivers/cpufreq/ia64-acpi-cpufreq.c b/drivers/cpufreq/ia64-acpi-cpufreq.c
index e28a31a40829..a757c0a1e7b5 100644
--- 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