Re: frequent lockups in 3.18rc4

From: Al Viro
Date: Sat Dec 13 2014 - 22:14:52 EST

On Sat, Dec 13, 2014 at 05:35:17PM -0800, Linus Torvalds wrote:
> On Sat, Dec 13, 2014 at 4:33 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > So does SMP - this_cpu_dec() relies on preemption being disabled.
> No. really. It very much does not. Not on x86, not elsewhere. It's
> part of the whole point of "this_cpu_p()". They are preemption and
> interrupt safe.
> It's the "__this_cpu_op()" ones that need external protection.

Right you are - I really need to get some coffee... Sorry...

FWIW, do we need to disable interrupts there? After all, mnt_want_write()
and mnt_drop_write() shouldn't be done from interrupt context - they can
happen via schedule_delayed_work(), but that's it...
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