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[66.111.4.228]) by smtp.gmail.com with ESMTPSA id k50-v6sm992315qtk.88.2018.06.26.03.39.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jun 2018 03:39:56 -0700 (PDT) Received: from compute6.internal (compute6.nyi.internal [10.202.2.46]) by mailauth.nyi.internal (Postfix) with ESMTP id C4D1621908; Tue, 26 Jun 2018 06:39:55 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute6.internal (MEProxy); Tue, 26 Jun 2018 06:39:55 -0400 X-ME-Sender: Received: from localhost (unknown [45.32.128.109]) by mail.messagingengine.com (Postfix) with ESMTPA id 8D8E7E407B; Tue, 26 Jun 2018 06:39:54 -0400 (EDT) Date: Tue, 26 Jun 2018 18:44:47 +0800 From: Boqun Feng To: Peter Zijlstra Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org Subject: Re: [PATCH tip/core/rcu 2/2] rcu: Make expedited GPs handle CPU 0 being offline Message-ID: <20180626104447.GG9125@tardis> References: <20180625224308.GA10064@linux.vnet.ibm.com> <20180625224332.10596-2-paulmck@linux.vnet.ibm.com> <20180626093820.GG2494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HCdXmnRlPgeNBad2" Content-Disposition: inline In-Reply-To: <20180626093820.GG2494@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --HCdXmnRlPgeNBad2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jun 26, 2018 at 11:38:20AM +0200, Peter Zijlstra wrote: > On Mon, Jun 25, 2018 at 03:43:32PM -0700, Paul E. McKenney wrote: > > + preempt_disable(); > > + for_each_leaf_node_possible_cpu(rnp, cpu) { > > + if (cpu_is_offline(cpu)) /* Preemption disabled. */ > > + continue; >=20 > Create for_each_node_online_cpu() instead? Seems a bit pointless to > iterate possible mask only to then check it against the online mask. > Just iterate the online mask directly. >=20 > Or better yet, write this as: >=20 > preempt_disable(); > cpu =3D cpumask_next(rnp->grplo - 1, cpu_online_mask); > if (cpu > rnp->grphi) > cpu =3D WORK_CPU_UNBOUND; > queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); > preempt_enable(); >=20 > Which is what it appears to be doing. >=20 Make sense! Thanks ;-) Applied this and running a TREE03 rcutorture. If all go well, I will send the updated patch. Regards, Boqun > > + queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); > > + rnp->exp_need_flush =3D true; > > + break; > > + } > > + preempt_enable(); > > + if (!rnp->exp_need_flush) { /* All offline, report QSes. */ > > + queue_work(rcu_par_gp_wq, &rnp->rew.rew_work); > > + rnp->exp_need_flush =3D true; > > + } > > } > > =20 > > /* Wait for workqueue jobs (if any) to complete. */ > > --=20 > > 2.17.1 > >=20 --HCdXmnRlPgeNBad2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEj5IosQTPz8XU1wRHSXnow7UH+rgFAlsyGRkACgkQSXnow7UH +ri1SQf/X3ITEo/cU0FHDbMb6hayVbEJ9vrw03PuRR5dxbaWQfs+VMxs65BBs1Vy mWJYx+Hf5oSsSXn6DJshe429YsBDHdgmjVX7j+qiKoQKl55dFnpJqPQDFpMyXo87 8NQ5BsBfQZkX9AagGWst+iblJcaItG5rHExzDpvZZfY3PjKng1Tc7K5yhmPqqG6g 93Zj88Wy7fAva0ObmIDzmhBkQf/OBZlOZt4sYCL7HyfnUt+E/bwaW1VIwF6V1qJ1 Y0mWW1eMgcCbUlFVcoOt+7BZGzqPi/29FTAMpdNrvNXPeB1HKsgS04i5LKRutheX qkrDdkPrdiiZPHGOAYJsmZAIrMxd4A== =5QpE -----END PGP SIGNATURE----- --HCdXmnRlPgeNBad2--