"Hemanth V" <hemanthv@xxxxxx> writes:
>> ----- Original Message -----
>> From: "Kevin Hilman" <khilman@xxxxxxxxxxxxxxxxxxx>
>> To: "Pandita, Vikram" <vikram.pandita@xxxxxx>
>> Cc: <linux-omap@xxxxxxxxxxxxxxx>
>> Sent: Tuesday, August 11, 2009 8:57 PM
>> Subject: Re: Warnings: pm branch
>>
>>
>>> "Pandita, Vikram" <vikram.pandita@xxxxxx> writes:
>>>
>>>> Has anyone send these warning logs on the pm branch on kevin's tree [1]
>>>> This seems to be some issue in CpuIdle path with interrupts?
>>>>
>>>> <4>WARNING: at arch/arm/kernel/process.c:171 cpu_idle+0x60/0x88()
>>>> WARNING: at arch/arm/kernel/process.c:171 cpu_idle+0x60/0x88()
>>>> <d>Modules linked in:Modules linked in:
>>>> [<c0031344>] [<c0031344>] (unwind_backtrace+0x0/0xdc)
>>>> (unwind_backtrace+0x0/0xdc
>>>> ) from [<c0057a08>] from [<c0057a08>] (warn_slowpath_common+0x48/0x60)
>>>> (warn_slowpath_common+0x48/0x60)
>>>> [<c0057a08>] [<c0057a08>] (warn_slowpath_common+0x48/0x60)
>>>> (warn_slowpath_common
>>>> +0x48/0x60) from [<c002d204>] from [<c002d204>] (cpu_idle+0x60/0x88)
>>>> (cpu_idle+0x60/0x88)
>>>> [<c002d204>] [<c002d204>] (cpu_idle+0x60/0x88) (cpu_idle+0x60/0x88) from
>>>> [<c0008
>>>> a70>] from [<c0008a70>] (start_kernel+0x234/0x28c)
>>>> (start_kernel+0x234/0x28c)
>>>> [<c0008a70>] [<c0008a70>] (start_kernel+0x234/0x28c)
>>>> (start_kernel+0x234/0x28c)
>>>> from [<80008034>] from [<80008034>] (0x80008034)
>>>> (0x80008034)
>>>>
>>>
>>> Yes, I've seen it, but have yet to debug it.
>>>
>>> This warning is from the generic ARM idle loop reporting that the OMAP
>>> idle path is returning with IRQs disabled.
>>>
>>> Kevin
>>
>> I did some more debugging on this. I added the below instrumentation to
>> local_irq_disable to capture
>> the PC of the last call to local_irq_disable.
>>
>> extern unsigned long hem_pc;
>> register unsigned long current_pc asm ("pc");
>>
>> #define local_irq_disable() \
>> do { hem_pc = current_pc;raw_local_irq_disable();
>> trace_hardirqs_off(); } while (0)
>>
>>
>> When I set a breakpoint at the instruction pointing to
>> WARN_ON(irqs_disabled()) using
>> lauterbach and dump hem_pc, I see that the last call to irq_disable is
>> actuall from cpu_idle itself.
>> Looks like some recursion is happening. Does anyone have any inputs on this.
>>
>> void cpu_idle(void)
>> {
>>
>> local_fiq_enable();
>>
>> /* endless idle loop with no priority at all */
>> while (1) {
>> tick_nohz_stop_sched_tick(1);
>> leds_event(led_idle_start);
>> while (!need_resched()) {
>> #ifdef CONFIG_HOTPLUG_CPU
>> if (cpu_is_offline(smp_processor_id()))
>> cpu_die();
>> #endif
>>
>>>> local_irq_disable();
>>
>>
>> Thanks
>> Hemanth
>>
>
> Below patch seems to fix the issue.
The question remains, who is disabling interrupts?
If this patch works, someone is disabling interrupts between the
enable in this routine and the return of this function.
Kevin
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 8504a21..3014104 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -75,8 +75,10 @@ static void cpuidle_idle_call(void)
> #endif
> /* ask the governor for the next state */
> next_state = cpuidle_curr_governor->select(dev);
> +
> if (need_resched())
> - return;
> + goto out;
> +
> target_state = &dev->states[next_state];
>
> /* enter the state and update stats */
> @@ -91,6 +93,12 @@ static void cpuidle_idle_call(void)
> /* give the governor an opportunity to reflect on the outcome */
> if (cpuidle_curr_governor->reflect)
> cpuidle_curr_governor->reflect(dev);
> +
> + return;
> +
> +out:
> + local_irq_enable();
> + return;
> }
>
> /**
--
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