On 2016-04-27 03:15, Thomas Gleixner wrote:
> On Wed, 27 Apr 2016, Dong Aisheng wrote:
>> Why Stefan's patch works (checking irqs_disabled()) is because during kernel
>> time init, the irq is still not enabled. It fixes the issue indirectly.
>> See:
>> asmlinkage __visible void __init start_kernel(void)
>> {
>> /*
>> * Set up the scheduler prior starting any interrupts (such as the
>> * timer interrupt). Full topology setup happens at smp_init()
>> * time - but meanwhile we still have a functioning scheduler.
>> */
>> sched_init();
>> .............
>> time_init();
>> ..............
>> WARN(!irqs_disabled(), "Interrupts were enabled early\n");
>> early_boot_irqs_disabled = false;
>> local_irq_enable();
>> }
>>
>> The issue can only happen when PLL enable causes a schedule during
>> imx_clock_init().
>
> Calling a function which might sleep _BEFORE_ kernel_init() is wrong. Don't
> try to work around such an issue by doing magic irq_disabled() checks and busy
> loops. Fix the call site and be done with it.
What do you mean exactly by fix the call site? The patch I proposed
(https://lkml.org/lkml/2016/1/29/695) fixes the call site...
But I see Dong's argument here, irqs_disabled is the wrong way to figure
out whether we are in kernel_init. What is the right approach to
distinguish whether we are allowed to sleep?
--
Stefan
