From patchwork Thu Jan 5 03:40:00 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zqiang X-Patchwork-Id: 13089365 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 CCCFBC46467 for ; Thu, 5 Jan 2023 03:34:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230059AbjAEDek (ORCPT ); Wed, 4 Jan 2023 22:34:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229835AbjAEDej (ORCPT ); Wed, 4 Jan 2023 22:34:39 -0500 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C90064882C; Wed, 4 Jan 2023 19:34:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1672889678; x=1704425678; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=QUTlUNdOBhgTJmvcsTFaL20j9mIag+B96H14BJHxIUs=; b=LWLxoqFJQjpjnipVakjFtQl0YcsP9FOIXBMeA6eqz3G2a3kpUSjfYQTL aptaOtz71sO6QgjmzV+z9GIF1v/UUBWtuQUHjUSRuFk8TuilMgkf2zEq4 V+sl9Hmz16JTV20N4ndpR7NEwbnb3HoJj7qv/Ivt6ngJ55oXtdmPOsP/j vOlAVbAlHszvU52S8T7CdlSVqq9p7HLfuVm/ViDA/pbB52tXaM4YOkPzc ESI60UCtpJCr45d68+9GDax7Ejr/bX08uoYhrBD3mfyCJLa64ron2SxGP 5a8tth9lUhxzXAPHJLADh00mRMYij4HLg3tAt1PzDH+MF/eS2ghAnv7LM g==; X-IronPort-AV: E=McAfee;i="6500,9779,10580"; a="322177651" X-IronPort-AV: E=Sophos;i="5.96,301,1665471600"; d="scan'208";a="322177651" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Jan 2023 19:34:38 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10580"; a="779428061" X-IronPort-AV: E=Sophos;i="5.96,301,1665471600"; d="scan'208";a="779428061" Received: from zq-optiplex-7090.bj.intel.com ([10.238.156.129]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Jan 2023 19:34:35 -0800 From: Zqiang To: paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] rcu: Rework tick dependency setting into rcu_exp_handler() Date: Thu, 5 Jan 2023 11:40:00 +0800 Message-Id: <20230105034000.971748-1-qiang1.zhang@intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Currently, when first find out the expedited grace period is not end and timeout occurred, we set tick dependency for CPUs that have not yet reported the quiescent state in the rcu_node structure's->expmask but need to eliminate races between set and clear tick dependency, setting CPU tick dependency need to hold rcu_node structure's->lock. This commit move tick dependency setting into rcu_exp_handler(), set tick dependency when fail to report a quiescent state and clear tick dependency in rcu_report_exp_rdp(). [from Frederic Weisbecker suggestion] Signed-off-by: Zqiang --- kernel/rcu/tree_exp.h | 43 ++++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 23 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 7cc4856da081..f1e947675727 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -586,39 +586,16 @@ static bool synchronize_rcu_expedited_wait_once(long tlimit) static void synchronize_rcu_expedited_wait(void) { int cpu; - unsigned long j; unsigned long jiffies_stall; unsigned long jiffies_start; unsigned long mask; int ndetected; - struct rcu_data *rdp; struct rcu_node *rnp; struct rcu_node *rnp_root = rcu_get_root(); - unsigned long flags; trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait")); jiffies_stall = rcu_exp_jiffies_till_stall_check(); jiffies_start = jiffies; - if (tick_nohz_full_enabled() && rcu_inkernel_boot_has_ended()) { - if (synchronize_rcu_expedited_wait_once(1)) - return; - rcu_for_each_leaf_node(rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - mask = READ_ONCE(rnp->expmask); - for_each_leaf_node_cpu_mask(rnp, cpu, mask) { - rdp = per_cpu_ptr(&rcu_data, cpu); - if (rdp->rcu_forced_tick_exp) - continue; - rdp->rcu_forced_tick_exp = true; - if (cpu_online(cpu)) - tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP); - } - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } - j = READ_ONCE(jiffies_till_first_fqs); - if (synchronize_rcu_expedited_wait_once(j + HZ)) - return; - } for (;;) { if (synchronize_rcu_expedited_wait_once(jiffies_stall)) @@ -729,6 +706,24 @@ static void rcu_exp_sel_wait_wake(unsigned long s) #ifdef CONFIG_PREEMPT_RCU +static void rcu_exp_set_tickdep(struct rcu_data *rdp) +{ + int cpu = rdp->cpu; + + if (tick_nohz_full_cpu(cpu) && rcu_inkernel_boot_has_ended() && + cpu_online(cpu)) { + /* + * The rcu_exp_handler() can be invoked from stop machine, + * at this time CPU has disabled all interrupts and offline, + * in which case, we don't need requeue IPI or irq work. + * which is not a problem since rcu_report_dead() does the + * QS report. + */ + rdp->rcu_forced_tick_exp = true; + tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP); + } +} + /* * Remote handler for smp_call_function_single(). If there is an * RCU read-side critical section in effect, request that the @@ -757,6 +752,7 @@ static void rcu_exp_handler(void *unused) WRITE_ONCE(rdp->cpu_no_qs.b.exp, true); set_tsk_need_resched(t); set_preempt_need_resched(); + rcu_exp_set_tickdep(rdp); } return; } @@ -778,6 +774,7 @@ static void rcu_exp_handler(void *unused) if (rnp->expmask & rdp->grpmask) { WRITE_ONCE(rdp->cpu_no_qs.b.exp, true); t->rcu_read_unlock_special.b.exp_hint = true; + rcu_exp_set_tickdep(rdp); } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return;