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McKenney" To: Peter Zijlstra Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, 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, rostedt@goodmis.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: <1cdbb0f6-9078-4023-bf37-8d826ca0c711@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> <87lear4wj6.fsf@oracle.com> <46a4c47a-ba1c-4776-a6f8-6c2146cbdd0d@paulmck-laptop> <31d50051-e42c-4ef2-a1ac-e45370c3752e@paulmck-laptop> <20231121203049.GN8262@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231121203049.GN8262@noisy.programming.kicks-ass.net> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 9797CA000F X-Stat-Signature: 338a36y4sju8po4p9m6wxhop8n3rujjr X-Rspam-User: X-HE-Tag: 1700601258-45908 X-HE-Meta: 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 w5VkBpcH 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 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 Tue, Nov 21, 2023 at 09:30:49PM +0100, Peter Zijlstra wrote: > On Tue, Nov 21, 2023 at 11:25:18AM -0800, Paul E. McKenney wrote: > > #define preempt_enable() \ > > do { \ > > barrier(); \ > > if (!IS_ENABLED(CONFIG_PREEMPT_RCU) && raw_cpu_read(rcu_data.rcu_urgent_qs) && \ > > (preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK | HARDIRQ_MASK | NMI_MASK) == PREEMPT_OFFSET) && > > !irqs_disabled()) \ > > rcu_all_qs(); \ > > if (unlikely(preempt_count_dec_and_test())) { \ > > __preempt_schedule(); \ > > } \ > > } while (0) > > Aaaaahhh, please no. We spend so much time reducing preempt_enable() to > the minimal thing it is today, this will make it blow up into something > giant again. IPIs, then. Or retaining some cond_resched() calls, as needed. Or is there another way? Thanx, Paul