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Date: Thu, 9 Nov 2017 18:30:27 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Davidlohr Bueso <dave@...olabs.net> Cc: Boqun Feng <boqun.feng@...il.com>, Andreas Dilger <adilger@...ger.ca>, Jan Kara <jack@...e.cz>, Waiman Long <longman@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.com>, Jeff Layton <jlayton@...chiereds.net>, "J. Bruce Fields" <bfields@...ldses.org>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux-foundation.org>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Andi Kleen <andi@...stfloor.org>, Dave Chinner <dchinner@...hat.com> Subject: Re: [PATCH v4] lib/dlock-list: Scale dlock_lists_empty() On Thu, Nov 09, 2017 at 09:24:08AM -0800, Davidlohr Bueso wrote: > On Wed, 08 Nov 2017, Boqun Feng wrote: > > Or worse: > > > > * CPU0 CPU1 > > * dlock_list_add() dlock_lists_empty() > > * smp_mb__before_atomic(); > > * [L] atomic_read(used_lists) Note that this is broken; smp_mb__before_atomic() is not valid on atomic_read(). > > * [S] atomic_inc(used_lists); > > * smp_mb__after_atomic(); > >
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