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McKenney" 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: <20231121203049.GN8262@noisy.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 0192040028 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: ugxu4c6xjy57mopqiifzs9qj7n1rpsr6 X-HE-Tag: 1700598687-172837 X-HE-Meta: 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 F67/G64a vyV8anOn3lmTvHnZFbFN3l1AWvudLp2+PzfJLEA/yGPZmbnuZk1cnFWB88/+K3OTGgKmlIL2vdeOmtCC1F97HRmlFByyRzJL/SJo7HfbLQzTcra0EFTw7P3ocVGDUDv6mzX6s6lF269gcpiWD1Pb0KWc0Z8HBNZ/MVNf2aglnevrez+irLyH25I5Vog== 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 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.