Re: start_kernel(): bug: interrupts were enabled early

Yinghai Lu
2010-03-31T20:49:22Z

On 03/31/2010 01:40 PM, Andrew Morton wrote:
> On Fri, 26 Mar 2010 01:11:00 +0530
> Rabin Vincent <rabin@rab.in> wrote:
>
>> > On latest git, I'm seeing "start_kernel(): bug: interrupts were enabled
>> > early" messages on ARM (sample log below).
>> >
>> > This appears to be caused by:
>> >
>> > start_kernel -> radix_tree_init -> kmem_cache_create (slub) ->
>> > down_write -> __down_write (lib/rwsem-spinlock.c) -> spin_unlock_irq
>> >
>> > radix_tree_init was moved earlier by:
>> >
>> > commit 773e3eb7b81e5ba13b5155dfb3bb75b8ce37f8f9
>> > Author: Yinghai Lu <yinghai@kernel.org>
>> > Date: Wed Feb 10 01:20:33 2010 -0800
>> >
>> > init: Move radix_tree_init() early
>> >
>> > Prepare for using radix trees in early_irq_init().
>> >
>> > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>> > LKML-Reference: <1265793639-15071-30-git-send-email-yinghai@kernel.org>
>> > Signed-off-by: H. Peter Anvin <hpa@zytor.com>
>> >
> That's going to be hard to fix.
>
> Once upon a time, enabling interrupts too early in boot would kill
> powerpc boxes stone dead. From the lack of noise I assume that this is
> not happening in current kernels for some reason.
>
> We have two checks in start_kernel():
>
> if (!irqs_disabled()) {
> printk(KERN_WARNING "start_kernel(): bug: interrupts were "
> "enabled *very* early, fixing it\n");
> local_irq_disable();
> }
> rcu_init();
> radix_tree_init();
> /* init some links before init_ISA_irqs() */
> early_irq_init();
> init_IRQ();
> prio_tree_init();
> init_timers();
> hrtimers_init();
> softirq_init();
> timekeeping_init();
> time_init();
> profile_init();
> if (!irqs_disabled())
> printk(KERN_CRIT "start_kernel(): bug: interrupts were "
> "enabled early\n");
>
> perhaps the second one isn't needed? Perhaps no architecture requires
> that local interrupts be disabled across the above initialisations?

spin_unlock_irq from arm is different from other archs?

YH