On 10/07/2012 11:26 PM, Rafael J. Wysocki wrote:
On Tuesday 25 of September 2012 00:43:54 Daniel Lezcano wrote:
With the tegra3 and the big.LITTLE [1] new architectures, several cpus with different characteristics (latencies and states) can co-exists on the system.
The cpuidle framework has the limitation of handling only identical cpus.
This patch removes this limitation by introducing the multiple driver support for cpuidle.
This option is configurable at compile time and should be enabled for the architectures mentioned above. So there is no impact for the other platforms if the option is disabled. The option defaults to 'n'. Note the multiple drivers support is also compatible with the existing drivers, even if just one driver is needed, all the cpu will be tied to this driver using an extra small chunk of processor memory.
The multiple driver support use a per-cpu driver pointer instead of a global variable and the accessor to this variable are done from a cpu context.
Thanks Rafael for the review.
I took into account all your remarks for the V2.
[ cut ]
+static int __cpuidle_register_all_cpu_driver(struct cpuidle_driver *drv) +{
- int ret = 0;
- int i, cpu;
- for_each_present_cpu(cpu) {
ret = __cpuidle_register_driver(drv, cpu);if (!ret)continue;for (i = cpu - 1; i >= 0; i--)I wonder if this is going to work in all cases. For example, is there any guarantee that the CPU numbers start from 0 and that there are no gaps?
AFAICS, the cpumask.h is not assuming the cpu numbers start from zero and they are contiguous.
I will fix this reverse loop, thanks for spotting this.
[ cut ]
void cpuidle_unregister_driver(struct cpuidle_driver *drv) { spin_lock(&cpuidle_driver_lock);
- __cpuidle_unregister_driver(drv);
+#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
- __cpuidle_unregister_all_cpu_driver(drv);
+#else
- __cpuidle_unregister_driver(drv, smp_processor_id());
+#endif
I'm slightly cautious about using smp_processor_id() above. get_cpu()/put_cpu() is the preferred way of doing this nowadays (although this particular code is under the spinlock, so it should be OK).
yes, get_cpu does preempt_disable() and smp_processor_id() As spin_lock does also preempt_disable() that should be ok. But I changed the code to use the preferred way.
Thanks -- Daniel