Re: [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t

[Sergey Senozhatsky]

On (20/12/09 09:16), Peter Zijlstra wrote:
> On Tue, Dec 08, 2020 at 11:36:44PM +0106, John Ogness wrote:
> > For the state variable we chose atomic_long_t instead of atomic64_t for
> > this reason. atomic_long_t operations are available atomically on all
> > architectures.
> 
> Please put on your eye cancer gear and inspect the atomic implementation
> of PA-RISC, Sparc32, feh, I forgot who else.
> 
> Those SMP capable architectures are gifted with just one XCHG like
> atomic instruction :/ Anyway, as said in the other email, they also
> don't have NMIs so it mostly works.

Hmm, wow. OK, I definitely want to look further.

When some CONFIG_DEBUG_FOO_BAR code wants to pr_err from prb->atomic_op
on those archs then we deadlock in printk once again?

	-ss