cpumask: use work_on_cpu in acpi/cstate.c

Impact: use new cpumask API to reduce stack usage

Replace the saving of current->cpus_allowed and set_cpus_allowed_ptr() with
a work_on_cpu function for the acpi_processor_ffh_cstate_probe() function.

Basically splits acpi_processor_ffh_cstate_probe() into two functions, the
other being acpi_processor_ffh_cstate_probe_cpu which is the work function
run on the designated cpu.
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/acpi/cstate.c

@@ -66,35 +66,15 @@ static short mwait_supported[ACPI_PROCESSOR_MAX_POWER];
 
 #define NATIVE_CSTATE_BEYOND_HALT	(2)
 
-int acpi_processor_ffh_cstate_probe(unsigned int cpu,
-		struct acpi_processor_cx *cx, struct acpi_power_register *reg)
+static long acpi_processor_ffh_cstate_probe_cpu(void *_cx)
 {
-	struct cstate_entry *percpu_entry;
-	struct cpuinfo_x86 *c = &cpu_data(cpu);
-
-	cpumask_t saved_mask;
-	int retval;
+	struct acpi_processor_cx *cx = _cx;
+	long retval;
 	unsigned int eax, ebx, ecx, edx;
 	unsigned int edx_part;
 	unsigned int cstate_type; /* C-state type and not ACPI C-state type */
 	unsigned int num_cstate_subtype;
 
-	if (!cpu_cstate_entry || c->cpuid_level < CPUID_MWAIT_LEAF )
-		return -1;
-
-	if (reg->bit_offset != NATIVE_CSTATE_BEYOND_HALT)
-		return -1;
-
-	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
-	percpu_entry->states[cx->index].eax = 0;
-	percpu_entry->states[cx->index].ecx = 0;
-
-	/* Make sure we are running on right CPU */
-	saved_mask = current->cpus_allowed;
-	retval = set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-	if (retval)
-		return -1;
-
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 
 	/* Check whether this particular cx_type (in CST) is supported or not */
@@ -114,21 +94,45 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
 		retval = -1;
 		goto out;
 	}
-	percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK;
-
-	/* Use the hint in CST */
-	percpu_entry->states[cx->index].eax = cx->address;
 
 	if (!mwait_supported[cstate_type]) {
 		mwait_supported[cstate_type] = 1;
-		printk(KERN_DEBUG "Monitor-Mwait will be used to enter C-%d "
+		printk(KERN_DEBUG
+			"Monitor-Mwait will be used to enter C-%d "
 			"state\n", cx->type);
 	}
-	snprintf(cx->desc, ACPI_CX_DESC_LEN, "ACPI FFH INTEL MWAIT 0x%x",
+	snprintf(cx->desc,
+			ACPI_CX_DESC_LEN, "ACPI FFH INTEL MWAIT 0x%x",
 			cx->address);
-
 out:
-	set_cpus_allowed_ptr(current, &saved_mask);
+	return retval;
+}
+
+int acpi_processor_ffh_cstate_probe(unsigned int cpu,
+		struct acpi_processor_cx *cx, struct acpi_power_register *reg)
+{
+	struct cstate_entry *percpu_entry;
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+	long retval;
+
+	if (!cpu_cstate_entry || c->cpuid_level < CPUID_MWAIT_LEAF)
+		return -1;
+
+	if (reg->bit_offset != NATIVE_CSTATE_BEYOND_HALT)
+		return -1;
+
+	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
+	percpu_entry->states[cx->index].eax = 0;
+	percpu_entry->states[cx->index].ecx = 0;
+
+	/* Make sure we are running on right CPU */
+
+	retval = work_on_cpu(cpu, acpi_processor_ffh_cstate_probe_cpu, cx);
+	if (retval == 0) {
+		/* Use the hint in CST */
+		percpu_entry->states[cx->index].eax = cx->address;
+		percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK;
+	}
 	return retval;
 }
 EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);