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SubjectRe: 2.6.27-rc4: lots of 'in_atomic():1, irqs_disabled():0' with software-raid1
On Fri, 29 Aug 2008 17:36:08 +1000 Neil Brown <neilb@suse.de> wrote:

> On Thursday August 28, akpm@linux-foundation.org wrote:
> >
> > I'm curious about how this happened.
> >
> > afaict from reading the code, this:
> >
> > rcu_read_lock();
> > might_sleep();
> > rcu_read_unlock();
> >
> > will warn if CONFIG_PREEMPT_RCU=n but won't warn if
> > CONFIG_PREEMPT_RCU=y. If correct, that's a nasty trap.
> >
> > Is that what you did?
>
> Uhm..
> $ grep PREEMPT /home/src/md-x86-64/.config
> CONFIG_PREEMPT_NONE=y
> # CONFIG_PREEMPT_VOLUNTARY is not set
> # CONFIG_PREEMPT is not set
> $ grep DEBUG_SPIN /home/src/md-x86-64/.config
> CONFIG_DEBUG_SPINLOCK=y
> CONFIG_DEBUG_SPINLOCK_SLEEP=y
> $ grep RCU /home/src/md-x86-64/.config
> CONFIG_CLASSIC_RCU=y
> # CONFIG_RCU_TORTURE_TEST is not set
>
> This definitely doesn't report an error if I put "might_sleep" inside
> rcu_read_lock. I tried to figure out why but got lost.

CONFIG_DEBUG_SPINLOCK_SLEEP doesn't do much useful without
CONFIG_PREEMPT=y. Perhaps we could improve the Kconfig situation
there.

The most fine Documentation/SubmitChecklist instructeth:

12: Has been tested with CONFIG_PREEMPT, CONFIG_DEBUG_PREEMPT,
CONFIG_DEBUG_SLAB, CONFIG_DEBUG_PAGEALLOC, CONFIG_DEBUG_MUTEXES,
CONFIG_DEBUG_SPINLOCK, CONFIG_DEBUG_SPINLOCK_SLEEP all simultaneously
enabled.

(which might need updating for new goodies - it was written a while ago).



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