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Date:   Thu, 30 May 2019 11:50:39 +0200
From:   Andrea Parri <andrea.parri@amarulasolutions.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     David Howells <dhowells@redhat.com>, viro@zeniv.linux.org.uk,
        raven@themaw.net, linux-fsdevel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-block@vger.kernel.org,
        keyrings@vger.kernel.org, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will.deacon@arm.com>,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH 1/7] General notification queue with user mmap()'able
 ring buffer
Message-ID: <20190530095039.GA5137@andrea>
References: <20190528231218.GA28384@kroah.com>
 <20190528162603.GA24097@kroah.com>
 <155905930702.7587.7100265859075976147.stgit@warthog.procyon.org.uk>
 <155905931502.7587.11705449537368497489.stgit@warthog.procyon.org.uk>
 <4031.1559064620@warthog.procyon.org.uk>
 <31936.1559146000@warthog.procyon.org.uk>
 <20190529231112.GB3164@kroah.com>
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> > Looking at the perf ring buffer, there appears to be a missing barrier in
> > perf_aux_output_end():
> > 
> > 	rb->user_page->aux_head = rb->aux_head;
> > 
> > should be:
> > 
> > 	smp_store_release(&rb->user_page->aux_head, rb->aux_head);
> > 
> > It should also be using smp_load_acquire().  See
> > Documentation/core-api/circular-buffers.rst
> > 
> > And a (partial) patch has been proposed: https://lkml.org/lkml/2018/5/10/249
> 
> So, if that's all that needs to be fixed, can you use the same
> buffer/code if that patch is merged?

That's about one year old...: let me add the usual suspects in Cc:  ;-)
since I'm not sure what the plan was (or if I'm missing something) ...

Speaking of ring buffer implementations (and relatively "old" patches),
here's another quite interesting:

  https://lkml.kernel.org/r/20181211034032.32338-1-yuleixzhang@tencent.com

Thanks,
  Andrea