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Date:   Thu, 13 Aug 2020 15:32:21 +0100
From:   Matthew Wilcox <>
To:     Thomas Gleixner <>
Cc:     Michal Hocko <>,
        Uladzislau Rezki <>,,
        LKML <>, RCU <>,, Andrew Morton <>,
        Vlastimil Babka <>,
        "Theodore Y . Ts'o" <>,
        Joel Fernandes <>,
        Sebastian Andrzej Siewior <>,
        Oleksiy Avramchenko <>
Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

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:

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

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

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