From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84F02C433FE for ; Tue, 19 Apr 2022 00:07:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238016AbiDSAKh (ORCPT ); Mon, 18 Apr 2022 20:10:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237868AbiDSAKe (ORCPT ); Mon, 18 Apr 2022 20:10:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94660B07; Mon, 18 Apr 2022 17:07:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2A5706123D; Tue, 19 Apr 2022 00:07:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76F23C385B0; Tue, 19 Apr 2022 00:07:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650326869; bh=Odu9Jp/hxYy/VMF9e4eVFNWBvKvfuFd+U74qxGLF8ng=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=clxgJoQ2pEzdSST8FXA+gyHzn/G2LU7vD7i7iM0uipY/ir+lmMpvulhzmgpGJOd2F zI6WUl8eAeCSH4kQLRMPUZ8OsR8o48Sp9x+9C4CacEmhzXP7ihFqkoNDe2xhydJXSF 70FUyxY4HqTQSg6MO1kuvfQwp0YVl3NGtvq/IFNtnNyPh6SJg1VprzaLUE0GwQwiA5 Ck08ROzo6lyJpR8uRsAmPOTun7gkLbUinV6wPt4zxcvHDrlvuXxG8R4WN6/HNJidSf l36nrmgK3sMKc4047KU2Tv+HpOnvpscSD/pFkKC88tSPKBa7+JicNYz1PvFhsCy6gr EdYh/SQC0EXkA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 2263A5C03F4; Mon, 18 Apr 2022 17:07:49 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" Subject: [PATCH rcu 2/6] rcutorture: Suppress debugging grace period delays during flooding Date: Mon, 18 Apr 2022 17:07:42 -0700 Message-Id: <20220419000746.3949667-2-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220419000541.GA3949109@paulmck-ThinkPad-P17-Gen-1> References: <20220419000541.GA3949109@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tree RCU supports grace-period delays using the rcutree.gp_cleanup_delay, rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot parameters. These delays are strictly for debugging purposes, and have proven quite effective at exposing bugs involving race with CPU-hotplug operations. However, these delays can result in false positives when used in conjunction with callback flooding, for example, those generated by the rcutorture.fwd_progress kernel boot parameter. This commit therefore suppresses grace-period delays while callback flooding is in progress. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 4 ++++ kernel/rcu/rcutorture.c | 4 ++++ kernel/rcu/tree.c | 32 +++++++++++++++++++++++++++++--- 3 files changed, 37 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 24b5f2c2de87..7a221393fcdb 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -523,6 +523,8 @@ static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { ret static inline void show_rcu_gp_kthreads(void) { } static inline int rcu_get_gp_kthreads_prio(void) { return 0; } static inline void rcu_fwd_progress_check(unsigned long j) { } +static inline void rcu_gp_slow_register(atomic_t *rgssp) { } +static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { } #else /* #ifdef CONFIG_TINY_RCU */ bool rcu_dynticks_zero_in_eqs(int cpu, int *vp); unsigned long rcu_get_gp_seq(void); @@ -535,6 +537,8 @@ void rcu_fwd_progress_check(unsigned long j); void rcu_force_quiescent_state(void); extern struct workqueue_struct *rcu_gp_wq; extern struct workqueue_struct *rcu_par_gp_wq; +void rcu_gp_slow_register(atomic_t *rgssp); +void rcu_gp_slow_unregister(atomic_t *rgssp); #endif /* #else #ifdef CONFIG_TINY_RCU */ #ifdef CONFIG_RCU_NOCB_CPU diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 55d049c39608..f37b7a01dcd0 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2916,10 +2916,12 @@ rcu_torture_cleanup(void) pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier); cur_ops->cb_barrier(); } + rcu_gp_slow_unregister(NULL); return; } if (!cur_ops) { torture_cleanup_end(); + rcu_gp_slow_unregister(NULL); return; } @@ -3016,6 +3018,7 @@ rcu_torture_cleanup(void) else rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); torture_cleanup_end(); + rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay); } #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD @@ -3320,6 +3323,7 @@ rcu_torture_init(void) if (object_debug) rcu_test_debug_objects(); torture_init_end(); + rcu_gp_slow_register(&rcu_fwd_cb_nodelay); return 0; unwind: diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a4b8189455d5..db67dae8ed88 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1705,11 +1705,37 @@ static void note_gp_changes(struct rcu_data *rdp) rcu_gp_kthread_wake(); } +static atomic_t *rcu_gp_slow_suppress; + +/* Register a counter to suppress debugging grace-period delays. */ +void rcu_gp_slow_register(atomic_t *rgssp) +{ + WARN_ON_ONCE(rcu_gp_slow_suppress); + + WRITE_ONCE(rcu_gp_slow_suppress, rgssp); +} +EXPORT_SYMBOL_GPL(rcu_gp_slow_register); + +/* Unregister a counter, with NULL for not caring which. */ +void rcu_gp_slow_unregister(atomic_t *rgssp) +{ + WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress); + + WRITE_ONCE(rcu_gp_slow_suppress, NULL); +} +EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister); + +static bool rcu_gp_slow_is_suppressed(void) +{ + atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress); + + return rgssp && atomic_read(rgssp); +} + static void rcu_gp_slow(int delay) { - if (delay > 0 && - !(rcu_seq_ctr(rcu_state.gp_seq) % - (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) + if (!rcu_gp_slow_is_suppressed() && delay > 0 && + !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) schedule_timeout_idle(delay); } -- 2.31.1.189.g2e36527f23