On 03/30/2012 05:15 PM, Daniel Lezcano wrote:
On 03/30/2012 01:25 PM, Srivatsa S. Bhat wrote:
On 03/30/2012 04:18 PM, Daniel Lezcano wrote:
The usual cpuidle initialization routines are to register the driver, then register a cpuidle device per cpu.
With the device's state count default initialization with the driver's state count, the code initialization remains mostly the same in the different drivers.
We can then add a new function 'cpuidle_register' where we register the driver and the devices. These devices can be defined in a global static variable in cpuidle.c. We will be able to factor out and remove a lot of duplicate lines of code.
As we still have some drivers, with different initialization routines, we keep 'cpuidle_register_driver' and 'cpuidle_register_device' as low level initialization routines to do some specific operations on the cpuidle devices.
Signed-off-by: Daniel Lezcanodaniel.lezcano@linaro.org
drivers/cpuidle/cpuidle.c | 34 ++++++++++++++++++++++++++++++++++ include/linux/cpuidle.h | 3 +++ 2 files changed, 37 insertions(+), 0 deletions(-)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index b8a1faf..2a174e8 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -23,6 +23,7 @@ #include "cpuidle.h"
DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices); +DEFINE_PER_CPU(struct cpuidle_device, cpuidle_device);
DEFINE_MUTEX(cpuidle_lock); LIST_HEAD(cpuidle_detected_devices); @@ -391,6 +392,39 @@ int cpuidle_register_device(struct cpuidle_device *dev)
EXPORT_SYMBOL_GPL(cpuidle_register_device);
+int cpuidle_register(struct cpuidle_driver *drv) +{
- int ret, cpu;
- struct cpuidle_device *dev;
- ret = cpuidle_register_driver(drv);
- if (ret)
return ret;- for_each_online_cpu(cpu) {
dev =&per_cpu(cpuidle_device, cpu);dev->cpu = cpu;ret = cpuidle_register_device(dev);if (ret)goto out_unregister;- }
Isn't this racy with respect to CPU hotplug?
No, I don't think so. Do you see a race ?
Well, that depends on when/where this function gets called. This patch introduces the function. Where is the caller?
As of now, if you are calling this in boot-up code, its not racy. However, there have been attempts to speed up boot times by trying to online cpus in parallel with the rest of the kernel initialization[1]. In that case, unless your call is an early init call, it can race with CPU hotplug.
[1]. https://lkml.org/lkml/2012/1/30/647
+out:
- return ret;
+out_unregister:
- for_each_online_cpu(cpu) {
dev =&per_cpu(cpuidle_device, cpu);cpuidle_unregister_device(dev);- }
This could be improved I guess.. What if the registration fails for the first cpu itself? Then looping over entire online cpumask would be a waste of time..
Certainly in a critical section that would make sense, but for 4,8 or 16 cpus in an initialization path at boot time... Anyway, I can add what is proposed in https://lkml.org/lkml/2012/3/22/143.
What about servers with a lot more CPUs, like say 128 or even more? :-)
Moreover I don't see any downsides to the optimization. So should be good to add it in any case...
Regards, Srivatsa S. Bhat
Here is a discussion on some very similar code: https://lkml.org/lkml/2012/3/22/72 https://lkml.org/lkml/2012/3/22/143
- cpuidle_unregister_driver(drv);
- goto out;
+} +EXPORT_SYMBOL_GPL(cpuidle_register);
- /**
- cpuidle_unregister_device - unregisters a CPU's idle PM feature
- @dev: the cpu
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index f3ebbba..17e3d33 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -133,6 +133,7 @@ struct cpuidle_driver { #ifdef CONFIG_CPU_IDLE extern void disable_cpuidle(void); extern int cpuidle_idle_call(void); +extern int cpuidle_register(struct cpuidle_driver *drv); extern int cpuidle_register_driver(struct cpuidle_driver *drv); struct cpuidle_driver *cpuidle_get_driver(void); extern void cpuidle_unregister_driver(struct cpuidle_driver *drv); @@ -150,6 +151,8 @@ extern int cpuidle_wrap_enter(struct cpuidle_device *dev, #else static inline void disable_cpuidle(void) { } static inline int cpuidle_idle_call(void) { return -ENODEV; } +static inline int cpuidle_register(struct cpuidle_driver *drv) +{return -ENODEV; } static inline int cpuidle_register_driver(struct cpuidle_driver *drv) {return -ENODEV; } static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }