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Tue, 31 Oct 2023 20:35:18 -0700 (PDT) From: Zqiang To: paulmck@kernel.org, frederic@kernel.org, joel@joelfernandes.org, boqun.feng@gmail.com Cc: qiang.zhang1211@gmail.com, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] rcu: Force quiescent states only for ongoing grace period Date: Wed, 1 Nov 2023 11:35:07 +0800 Message-Id: <20231101033507.21651-1-qiang.zhang1211@gmail.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Tue, 31 Oct 2023 20:35:34 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1781331219738062888 X-GMAIL-MSGID: 1781331219738062888 Currently, when running the rcutorture testing, if the fqs_task kthread was created, the periodic fqs operations will be performed, regardless of whether the grace-period is ongoing. however, if there is no ongoing grace-period, invoke the rcu_force_quiescent_state() has no effect, because when the new grace-period starting, will clear all flags int rcu_state.gp_flags in rcu_gp_init(). this commit therefore add rcu_gp_in_progress() check in rcu_force_quiescent_state(), if there is no ongoing grace-period, return directly. Signed-off-by: Zqiang --- kernel/rcu/tree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index aa4c808978b8..5b4279ef66da 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2338,6 +2338,8 @@ void rcu_force_quiescent_state(void) struct rcu_node *rnp; struct rcu_node *rnp_old = NULL; + if (!rcu_gp_in_progress()) + return; /* Funnel through hierarchy to reduce memory contention. */ rnp = raw_cpu_read(rcu_data.mynode); for (; rnp != NULL; rnp = rnp->parent) {