From patchwork Fri Dec 8 22:05:41 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 13485867 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8878A47A5E for ; Fri, 8 Dec 2023 22:06:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sfV0bAA3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2059C433CB; Fri, 8 Dec 2023 22:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702073164; bh=2VSL0I6CDQD3On48r7ZZl2KNfsOXx4qI+XGTjXvz4To=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sfV0bAA3jMUaWQ7vGD0VMm4RIRuqF0R57O6AyLWLuIz64dUmxfQpa8c1ga8kShpyW w/tmMOwatv3tjWq6lRY5NzU3lVvcHjTa6NLBBeUgAHOR9YdENAOSGYTgK3vs6pystc e+GqnbPLuT7sFWpY1mrdr55j099gb7C2lTMluQur4lQOFYzcWPm3r33wagwqn7AYZ+ e/T7zYVHXergvzndqp/awswOBzn26JxZhhw01hSmeGlJSJdxi6vwEHnWJaXdDV+f2f pSnEbC4NZlMyi2DCb3fYtdjlnztzoxJiLz6/recBTwHZpXndpdXAXKsgYKyHdhqKKM DQ/9wRlfXoBUQ== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Boqun Feng , Joel Fernandes , Neeraj Upadhyay , "Paul E . McKenney" , Uladzislau Rezki , Zqiang , rcu , Anna-Maria Behnsen , Thomas Gleixner , Kalesh Singh Subject: [PATCH 4/8] rcu/exp: Handle RCU expedited grace period kworker allocation failure Date: Fri, 8 Dec 2023 23:05:41 +0100 Message-ID: <20231208220545.7452-5-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231208220545.7452-1-frederic@kernel.org> References: <20231208220545.7452-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Just like is done for the kworker performing nodes initialization, gracefully handle the possible allocation failure of the RCU expedited grace period main kworker. While at it perform a rename of the related checking functions to better reflect the expedited specifics. Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker") Cc: Kalesh Singh Signed-off-by: Frederic Weisbecker Reviewed-by: Kalesh Singh --- kernel/rcu/tree.c | 2 ++ kernel/rcu/tree_exp.h | 25 +++++++++++++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 055f4817bc70..39679cf66c3a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4717,6 +4717,7 @@ static void __init rcu_start_exp_gp_kworkers(void) rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name); if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) { pr_err("Failed to create %s!\n", gp_kworker_name); + rcu_exp_gp_kworker = NULL; return; } @@ -4725,6 +4726,7 @@ static void __init rcu_start_exp_gp_kworkers(void) pr_err("Failed to create %s!\n", par_gp_kworker_name); rcu_exp_par_gp_kworker = NULL; kthread_destroy_worker(rcu_exp_gp_kworker); + rcu_exp_gp_kworker = NULL; return; } diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 6d7cea5d591f..cb31f4fb4b36 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -429,7 +429,12 @@ static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp) __sync_rcu_exp_select_node_cpus(rewp); } -static inline bool rcu_gp_par_worker_started(void) +static inline bool rcu_exp_worker_started(void) +{ + return !!READ_ONCE(rcu_exp_gp_kworker); +} + +static inline bool rcu_exp_par_worker_started(void) { return !!READ_ONCE(rcu_exp_par_gp_kworker); } @@ -479,7 +484,12 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) __sync_rcu_exp_select_node_cpus(rewp); } -static inline bool rcu_gp_par_worker_started(void) +static inline bool rcu_exp_worker_started(void) +{ + return !!READ_ONCE(rcu_gp_wq); +} + +static inline bool rcu_exp_par_worker_started(void) { return !!READ_ONCE(rcu_par_gp_wq); } @@ -542,7 +552,7 @@ static void sync_rcu_exp_select_cpus(void) rnp->exp_need_flush = false; if (!READ_ONCE(rnp->expmask)) continue; /* Avoid early boot non-existent wq. */ - if (!rcu_gp_par_worker_started() || + if (!rcu_exp_par_worker_started() || rcu_scheduler_active != RCU_SCHEDULER_RUNNING || rcu_is_last_leaf_node(rnp)) { /* No worker started yet or last leaf, do direct call. */ @@ -957,7 +967,7 @@ static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) */ void synchronize_rcu_expedited(void) { - bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT); + bool can_queue; unsigned long flags; struct rcu_exp_work rew; struct rcu_node *rnp; @@ -968,6 +978,9 @@ void synchronize_rcu_expedited(void) lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); + can_queue = (rcu_scheduler_active != RCU_SCHEDULER_INIT) && + rcu_exp_worker_started(); + /* Is the state is such that the call is a grace period? */ if (rcu_blocking_is_gp()) { // Note well that this code runs with !PREEMPT && !SMP. @@ -997,7 +1010,7 @@ void synchronize_rcu_expedited(void) return; /* Someone else did our work for us. */ /* Ensure that load happens before action based on it. */ - if (unlikely(boottime)) { + if (unlikely(!can_queue)) { /* Direct call during scheduler init and early_initcalls(). */ rcu_exp_sel_wait_wake(s); } else { @@ -1015,7 +1028,7 @@ void synchronize_rcu_expedited(void) /* Let the next expedited grace period start. */ mutex_unlock(&rcu_state.exp_mutex); - if (likely(!boottime)) + if (likely(can_queue)) synchronize_rcu_expedited_destroy_work(&rew); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);