Re: [PATCH] mm/tlb: Fix use_mm() vs TLB invalidate

From: Linus Torvalds
Date: Fri Feb 21 2020 - 14:19:43 EST

On Fri, Feb 21, 2020 at 3:11 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> + BUG_ON(!(tsk->flags & PF_KTHREAD));
> + BUG_ON(tsk->mm != NULL);

Stop this craziness.

There is absolutely ZERO excuse for this kind of garbage.

Making this a BUG_ON() will just cause all the possible debugging info
to be thrown away and lost, and you often have a dead machine.

For absolutely no good reason.

Make it a WARN_ON_ONCE(). If it triggers, everything works the way it
always did, but we get notified.

Stop with the stupid crazy BUG_ON() crap already. It is actively _bad_
for debugging.