Re: [PATCH v4 12/22] lib/stackdepot: use read/write lock

[Andi Kleen]

> stackdepot is severely limited in what kernel facilities it may use
> due to being used by such low level facilities as the allocator
> itself.

RCU can be done quite low level too (e.g. there is NMI safe RCU)

> 
> I've been suggesting percpu-rwsem here, but looking at it in more
> detail that doesn't work because percpu-rwsem wants to sleep, but
> stackdepot must work in non-sleepable contexts. :-/

Yes something per CPU would work too I suppose. We used to have
big reader spinlocks for this. 

-Andi