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McKenney" To: Steven Rostedt Cc: Ankur Arora , Thomas Gleixner , linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linux-foundation.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com Subject: Re: [RFC PATCH 48/86] rcu: handle quiescent states for PREEMPT_RCU=n Message-ID: <3cc64b80-0975-4cdf-81ea-952ca80976e4@paulmck-laptop> Reply-To: paulmck@kernel.org References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107215742.363031-49-ankur.a.arora@oracle.com> <2027da00-273d-41cf-b9e7-460776181083@paulmck-laptop> <87v89lzu5a.ffs@tglx> <209f0e89-7ebd-4759-9883-21d842d0d26c@paulmck-laptop> <87zfymn6h9.fsf@oracle.com> <20231206211022.710ada02@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231206211022.710ada02@gandalf.local.home> X-Rspamd-Queue-Id: A4FBA140013 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 9m9qp6iat9cwrxw8ms5kz948rebrsmbx X-HE-Tag: 1701923829-410062 X-HE-Meta: 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 sNImvXz6 FYxMkO57v7WaG/qXrlRb8+gtnkPX0m2owRikCzfdur/2CU66vy/PNG8kGpPAkSv1AXA8mYdtvEAZAbx9xWhovCjmR9CKq4MZTHGS3+LqgcJwB9PCJlupOFO6Z0qnUwWovg9SHjEuplOzXxi6eQfIHZXCBkF8uHfGYDOcx46Dbd6hFWOzvafZlVhsIthaSno3xM/EbmNqMYEY6TbVIz3109k/PrK4lePJ8wubT80ymhC5QbLWcTRKclgT4F/Kp0+iaQnIJzxJCWF9yUCivQU5JFs1QjeLzJsBlA1uKyHuesuM1QhGwtX7TCQLCsa7zW2r8ffstpLKlo66XfRCroWjbvxo3W4YKbgOcCrUq/WghBBVftCnxyH+hwflmkbM2P7EqyTsuCYEjrTcg0I8viKZ3faetxwN+/Ha8c2f0Jbdl1SZfVOi8l3jGqA80FTscD3NCQbcIGC6JHukSqNWRg9xFo5h7kNDtakOJCBzHWnYapWRlobYOyzblBBz79gbHfhTw5Qy50jT5ZBX60M2DggtTCvUsWqCJ9o4ajqJ3CCE4CyWZTWpzZZeZdDEjDA8Ig0nor1riNAfQosHZe20cnK3mfvaRiCUGA11M+cp0Z5K6MiKKtMk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Dec 06, 2023 at 09:10:22PM -0500, Steven Rostedt wrote: > On Wed, 06 Dec 2023 17:31:30 -0800 > Ankur Arora wrote: > > > --- > > diff --git a/include/linux/preempt.h b/include/linux/preempt.h > > index 9aa6358a1a16..d8139cda8814 100644 > > --- a/include/linux/preempt.h > > +++ b/include/linux/preempt.h > > @@ -226,9 +226,11 @@ do { \ > > #ifdef CONFIG_PREEMPTION > > #define preempt_enable() \ > > do { \ > > barrier(); \ > > if (unlikely(preempt_count_dec_and_test())) \ > > __preempt_schedule(); \ > > + else if (unlikely(raw_cpu_read(rcu_data.rcu_urgent_qs))) \ > > Shouldn't this still have the: > > else if (!IS_ENABLED(CONFIG_PREEMPT_RCU) && \ > > That is, is it needed when PREEMPT_RCU is set? Given that PREEMPT_RCU has been getting along fine without it, I agree with Steve on this one. Unless and until someone demonstrates otherwise, but such a demonstration would almost certainly affect current code, not just the lazy-preemption changes. Thanx, Paul > -- Steve > > > > + rcu_all_qs_check(); > > } while (0) > > > > #define preempt_enable_notrace() \