Re: Warnings: pm branch

["Hemanth V" <hemanthv@ti.com>]

----- Original Message ----- 
From: "Kevin Hilman" <khilman@deeprootsystems.com>
To: "Pandita, Vikram" <vikram.pandita@ti.com>
Cc: <linux-omap@vger.kernel.org>
Sent: Tuesday, August 11, 2009 8:57 PM
Subject: Re: Warnings: pm branch


> "Pandita, Vikram" <vikram.pandita@ti.com> 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