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Date:   Tue, 14 Jul 2020 21:40:31 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>, x86@kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Fenghua Yu <fenghua.yu@intel.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH 11/15] memremap: Add zone device access protection
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On Tue, Jul 14, 2020 at 12:10:47PM -0700, Ira Weiny wrote:
> On Tue, Jul 14, 2020 at 10:40:57AM +0200, Peter Zijlstra wrote:

> > That's an anti-pattern vs static_keys, I'm thinking you actually want
> > static_key_slow_{inc,dec}() instead of {enable,disable}().
> 
> Thanks.  I'll go read the doc for those as I'm not familiar with them.

Look for static_branch_{inc,dec} in include/linux/jump_label.h, it
basically does the refcount thing you need and does the actual
transition on the 0->1 and 1->0 transitions.