* Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> [2009-10-07 16:45:50]: > On Tue, 2009-10-06 at 21:01 +0530, Arun R Bharadwaj wrote: > > +++ linux.trees.git/arch/x86/kernel/process.c > > @@ -9,6 +9,7 @@ > > #include <linux/pm.h> > > #include <linux/clockchips.h> > > #include <linux/random.h> > > +#include <linux/cpuidle.h> > > #include <trace/events/power.h> > > #include <asm/system.h> > > #include <asm/apic.h> > > @@ -244,12 +245,6 @@ int sys_vfork(struct pt_regs *regs) > > unsigned long boot_option_idle_override = 0; > > EXPORT_SYMBOL(boot_option_idle_override); > > > > -/* > > - * Powermanagement idle function, if any.. > > - */ > > -void (*pm_idle)(void); > > -EXPORT_SYMBOL(pm_idle); > > - > > #ifdef CONFIG_X86_32 > > /* > > * This halt magic was a workaround for ancient floppy DMA > > @@ -329,17 +324,15 @@ static void do_nothing(void *unused) > > } > > > > /* > > - * cpu_idle_wait - Used to ensure that all the CPUs discard old value of > > - * pm_idle and update to new pm_idle value. Required while changing pm_idle > > - * handler on SMP systems. > > + * cpu_idle_wait - Required while changing idle routine handler on SMP systems. > > * > > - * Caller must have changed pm_idle to the new value before the call. Old > > - * pm_idle value will not be used by any CPU after the return of this function. > > + * Caller must have changed idle routine to the new value before the call. Old > > + * value will not be used by any CPU after the return of this function. > > */ > > void cpu_idle_wait(void) > > { > > smp_mb(); > > - /* kick all the CPUs so that they exit out of pm_idle */ > > + /* kick all the CPUs so that they exit out of idle loop */ > > smp_call_function(do_nothing, NULL, 1); > > } > > EXPORT_SYMBOL_GPL(cpu_idle_wait); > > @@ -518,15 +511,59 @@ static void c1e_idle(void) > > default_idle(); > > } > > > > +static void (*local_idle)(void); > > +DEFINE_PER_CPU(struct cpuidle_device, idle_devices); > > + > > +struct cpuidle_driver cpuidle_default_driver = { > > + .name = "cpuidle_default", > > +}; > > + > > +static int local_idle_loop(struct cpuidle_device *dev, struct cpuidle_state *st) > > +{ > > + ktime_t t1, t2; > > + s64 diff; > > + int ret; > > + > > + t1 = ktime_get(); > > + local_idle(); > > + t2 = ktime_get(); > > + > > + diff = ktime_to_us(ktime_sub(t2, t1)); > > + if (diff > INT_MAX) > > + diff = INT_MAX; > > + ret = (int) diff; > > + > > + return ret; > > +} > > + > > +static int setup_cpuidle_simple(void) > > +{ > > + struct cpuidle_device *dev; > > + int cpu; > > + > > + if (!cpuidle_curr_driver) > > + cpuidle_register_driver(&cpuidle_default_driver); > > + > > + for_each_online_cpu(cpu) { > > + dev = &per_cpu(idle_devices, cpu); > > + dev->cpu = cpu; > > + dev->states[0].enter = local_idle_loop; > > + dev->state_count = 1; > > + cpuidle_register_device(dev); > > + } > > + return 0; > > +} > > +device_initcall(setup_cpuidle_simple); > > + > > void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) > > { > > #ifdef CONFIG_SMP > > - if (pm_idle == poll_idle && smp_num_siblings > 1) { > > + if (local_idle == poll_idle && smp_num_siblings > 1) { > > printk(KERN_WARNING "WARNING: polling idle and HT enabled," > > " performance may degrade.\n"); > > } > > #endif > > - if (pm_idle) > > + if (local_idle) > > return; > > > > if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) { > > @@ -534,18 +571,20 @@ void __cpuinit select_idle_routine(const > > * One CPU supports mwait => All CPUs supports mwait > > */ > > printk(KERN_INFO "using mwait in idle threads.\n"); > > - pm_idle = mwait_idle; > > + local_idle = mwait_idle; > > } else if (check_c1e_idle(c)) { > > printk(KERN_INFO "using C1E aware idle routine\n"); > > - pm_idle = c1e_idle; > > + local_idle = c1e_idle; > > } else > > - pm_idle = default_idle; > > + local_idle = default_idle; > > + > > + return; > > } > > > > void __init init_c1e_mask(void) > > { > > /* If we're using c1e_idle, we need to allocate c1e_mask. */ > > - if (pm_idle == c1e_idle) > > + if (local_idle == c1e_idle) > > zalloc_cpumask_var(&c1e_mask, GFP_KERNEL); > > } > > > > @@ -556,7 +595,7 @@ static int __init idle_setup(char *str) > > > > if (!strcmp(str, "poll")) { > > printk("using polling idle threads.\n"); > > - pm_idle = poll_idle; > > + local_idle = poll_idle; > > } else if (!strcmp(str, "mwait")) > > force_mwait = 1; > > else if (!strcmp(str, "halt")) { > > @@ -567,7 +606,7 @@ static int __init idle_setup(char *str) > > * To continue to load the CPU idle driver, don't touch > > * the boot_option_idle_override. > > */ > > - pm_idle = default_idle; > > + local_idle = default_idle; > > idle_halt = 1; > > return 0; > > } else if (!strcmp(str, "nomwait")) { > > > What guarantees that the cpuidle bits actually select this > cpuidle_default driver when you do idle=poll? > When we do a idle=poll, it sets boot_option_idle_override = 1, which is checked during cpuidle_register_device in acpi/processor_idle.c So cpuidle devices are not even registered if this option is set. But, in acpi/processor_core.c where cpuidle_register_driver happens, this check is not made currently. So, I guess this check must be added before we register acpi_idle driver. > Also, cpuidle already has a poll loop in it, why duplicate that? > Suppose the arch doesnt have a poll loop of its own, it can use the one provided by cpuidle. I have just retained this from the earlier implementation. --arun -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html