| Message ID | 1309229190-25006-3-git-send-email-toddpoynor@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Todd Poynor <toddpoynor@google.com> writes: > Change-Id: Id833e61c13baa1783705ac9e9046d1f0cc90c95e > Signed-off-by: Todd Poynor <toddpoynor@google.com> I don't think the notifiers should be called in ARM-generic code. As discussed w/Colin in his proposal for the CPU PM notifiers, the platform-specific code should decide when to run notifier chain. To give an example, on OMAP we wouldn't want the notifier chain to be run until the OMAP PM core has programmed the next states of the various power domains. That way the notifier functions could check the next state to determine if their powerdomain is going to retention or off and decide whether or not a context save/restore will be needed. Kevin > --- > arch/arm/kernel/process.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c > index 5e1e541..1b9101e 100644 > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -184,6 +184,7 @@ void cpu_idle(void) > while (1) { > tick_nohz_stop_sched_tick(1); > leds_event(led_idle_start); > + idle_notifier_call_chain(IDLE_START); > while (!need_resched()) { > #ifdef CONFIG_HOTPLUG_CPU > if (cpu_is_offline(smp_processor_id())) > @@ -208,6 +209,7 @@ void cpu_idle(void) > } > } > leds_event(led_idle_end); > + idle_notifier_call_chain(IDLE_END); > tick_nohz_restart_sched_tick(); > preempt_enable_no_resched(); > schedule();
On Mon, Jun 27, 2011 at 07:46:29PM -0700, Todd Poynor wrote: > Change-Id: Id833e61c13baa1783705ac9e9046d1f0cc90c95e > Signed-off-by: Todd Poynor <toddpoynor@google.com> > --- > arch/arm/kernel/process.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c > index 5e1e541..1b9101e 100644 > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -184,6 +184,7 @@ void cpu_idle(void) > while (1) { > tick_nohz_stop_sched_tick(1); > leds_event(led_idle_start); > + idle_notifier_call_chain(IDLE_START); > while (!need_resched()) { > #ifdef CONFIG_HOTPLUG_CPU > if (cpu_is_offline(smp_processor_id())) > @@ -208,6 +209,7 @@ void cpu_idle(void) > } > } > leds_event(led_idle_end); > + idle_notifier_call_chain(IDLE_END); > tick_nohz_restart_sched_tick(); > preempt_enable_no_resched(); > schedule(); You seem to use this notifier with different semantics than x86. x86 notifies idle state when it knows it goes to sleep and exit it any time it gets interrupted. And it does that every time in the need_resched() loop. But here in ARM you enter idle only once before the loop (and you don't even know if you will enter the loop). And you don't notify idle exit state on interrupts. So if in the end this idle notifier is something that is really wanted, it needs to have a consistant behaviour across archs.
On Mon, Jul 11, 2011 at 09:50:04PM +0200, Frederic Weisbecker wrote: > On Mon, Jun 27, 2011 at 07:46:29PM -0700, Todd Poynor wrote: > > Change-Id: Id833e61c13baa1783705ac9e9046d1f0cc90c95e > > Signed-off-by: Todd Poynor <toddpoynor@google.com> > > --- > > arch/arm/kernel/process.c | 2 ++ > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c > > index 5e1e541..1b9101e 100644 > > --- a/arch/arm/kernel/process.c > > +++ b/arch/arm/kernel/process.c > > @@ -184,6 +184,7 @@ void cpu_idle(void) > > while (1) { > > tick_nohz_stop_sched_tick(1); > > leds_event(led_idle_start); > > + idle_notifier_call_chain(IDLE_START); > > while (!need_resched()) { > > #ifdef CONFIG_HOTPLUG_CPU > > if (cpu_is_offline(smp_processor_id())) > > @@ -208,6 +209,7 @@ void cpu_idle(void) > > } > > } > > leds_event(led_idle_end); > > + idle_notifier_call_chain(IDLE_END); > > tick_nohz_restart_sched_tick(); > > preempt_enable_no_resched(); > > schedule(); > > You seem to use this notifier with different semantics than x86. > x86 notifies idle state when it knows it goes to sleep and exit it any > time it gets interrupted. And it does that every time in the need_resched() > loop. > > But here in ARM you enter idle only once before the loop (and you don't even > know if you will enter the loop). And you don't notify idle exit state on interrupts. > > So if in the end this idle notifier is something that is really wanted, it needs > to have a consistant behaviour across archs. Yes, I didn't want to change the behavior of the existing notifiers being converted in these patches, but eventually one would want cross-arch idle callbacks with consistent behavior, and the existing arch-specific notifications have different semantics. My goal is to notify when the OS scheduler enters and exits its idle loop, so the existing ARM semantics are what I'm aiming for; the x86_64 behavior is probably further evidence that it is really a cpuidle-style operation being performed. If the idle notifiers do find any traction then it sounds like moving the notification to the common schedule code would be the right thing to do. Thanks -- Todd
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 5e1e541..1b9101e 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -184,6 +184,7 @@ void cpu_idle(void) while (1) { tick_nohz_stop_sched_tick(1); leds_event(led_idle_start); + idle_notifier_call_chain(IDLE_START); while (!need_resched()) { #ifdef CONFIG_HOTPLUG_CPU if (cpu_is_offline(smp_processor_id())) @@ -208,6 +209,7 @@ void cpu_idle(void) } } leds_event(led_idle_end); + idle_notifier_call_chain(IDLE_END); tick_nohz_restart_sched_tick(); preempt_enable_no_resched(); schedule();
Change-Id: Id833e61c13baa1783705ac9e9046d1f0cc90c95e Signed-off-by: Todd Poynor <toddpoynor@google.com> --- arch/arm/kernel/process.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)