-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kevin Hilman Sent: Wednesday, August 12, 2009 6:59 PM To: V, Hemanth Cc: Pandita, Vikram; [email protected] Subject: Re: Warnings: pm branch
"Hemanth V" <[email protected]> writes: >> ----- Original Message ----- >> From: "Kevin Hilman" <[email protected]> >> To: "Pandita, Vikram" <[email protected]> >> Cc: <[email protected]> >> Sent: Tuesday, August 11, 2009 8:57 PM >> Subject: Re: Warnings: pm branch >> >> >>> "Pandita, Vikram" <[email protected]> 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 It's disabled in cpu_idle function itself before calling pm_idle Here is the snap of cpu_idle 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(); //it's disabled here if (hlt_counter) { local_irq_enable(); cpu_relax(); } else { stop_critical_timings(); pm_idle(); start_critical_timings(); /* * This will eventually be removed - pm_idle * functions should always return with IRQs * enabled. */ WARN_ON(irqs_disabled()); local_irq_enable(); } } > 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; > } > > /** -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
