Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

[Matthew Wilcox]

On Thu, Aug 13, 2020 at 03:27:15PM +0200, Thomas Gleixner wrote:
> And guarding it with RT is not working either because then you are back
> to square one with the problem which triggered the discussion in the
> first place:
> 
> raw_spin_lock()
>   alloc()
>     if (RT && !preemptible())  <- False because RT == false
>     	goto bail;
> 
>     spin_lock(&zone->lock)  --> LOCKDEP complains
> 
> So either you convince Paul not to do that or you need to do something
> like I suggested in my other reply.

I'd like to throw in the possibility that we do something like:

  raw_spin_lock()
    alloc()
      if (!spin_trylock(&zone->lock))
        if (RT && !preemptible())
          goto bail;
        spin_lock(&zone->lock);

would that make us feel more comfortable about converting zone->lock to
a raw spinlock?