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McKenney" Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Ingo Molnar , Josh Triplett , Lai Jiangshan , Mathieu Desnoyers , Peter Zijlstra , Steven Rostedt Subject: Re: [PATCH RFC 1/2] sched/core: Convert synchronize_rcu_mult to synchronize_rcu Message-ID: <20181002212019.GC89166@joelaf.mtv.corp.google.com> References: <20181002012012.13133-1-joel@joelfernandes.org> <20181002033801.GP4222@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181002033801.GP4222@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 01, 2018 at 08:38:01PM -0700, Paul E. McKenney wrote: > On Mon, Oct 01, 2018 at 06:20:11PM -0700, Joel Fernandes wrote: > > From: "Joel Fernandes (Google)" > > > > synchronize_rcu_mult is now obsolete since all the different RCU flavors > > have been consolidated and the API is now common on the updater side. > > sched/core.c is the only user of it. All call_rcu_ calls boil > > down to the same call_rcu. So there's no point in calling > > synchronize_rcu_mult infact it could potentially be slower due to > > waiting for the call_rcu callback twice. Just call synchronize_rcu here > > which should do the job. > > > > Signed-off-by: Joel Fernandes (Google) > > Well, the theory was that I was going to keep this series hidden until > the consolidation hit mainline just to avoid confusion, but please see > 5fc9d4e000b1 ("rcu: Eliminate synchronize_rcu_mult()"), which I just > now pushed to -rcu. To your credit, you did get most of it. ;-) Glad you already took care of that ;-) I should have taken a peek at rcu/test branch :D > Here is the full list: > > pick 1f3e6eaed8fa Apply coccinelle script to consolidate calls to RCU-bh and RCU-sched > pick 5fc9d4e000b1 rcu: Eliminate synchronize_rcu_mult() > pick a8475496801e rcu: Consolidate the RCU update functions invoked by sync.c > pick d8ffb03461ad sched/membarrier: Replace synchronize_sched() with synchronize_rcu() > > Of course, I will need to rerun the coccinelle script and split the > result across subsystems, but I am waiting until the current pull > request hits mainline. Let's face it, none of us need to do debugging > on someone consolidating their RCU updates before at least this commit > and its predecessors hit mainline: > > 709fdce7545c ("rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched") > > I sent the pull request to Ingo a few days ago, so with some luck this > will all get to mainline during the next merge window, and then it is > open season on outside-of-RCU cleanups. ;-) Cool, thanks, - Joel