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 43F34C433EF for ; Tue, 26 Apr 2022 10:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349405AbiDZK6v (ORCPT ); Tue, 26 Apr 2022 06:58:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344991AbiDZK6e (ORCPT ); Tue, 26 Apr 2022 06:58:34 -0400 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C1D41ADA7; Tue, 26 Apr 2022 03:55:22 -0700 (PDT) Received: by mail-pg1-x529.google.com with SMTP id r83so15784579pgr.2; Tue, 26 Apr 2022 03:55:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1is8Iezkr6s4Ex2hsS25ZUz1zJxOesQz7FGVxmLzzqI=; b=idWnfBDCgrNUeljAqaXrAT4U6MHGcB4AZmSRDKAPosvQg3uh0UipKFopd2yHHL7I8X wQlCTR9svWEM7Hsm8hp36VcRC1aZikJR3va1xrKo8d/Hf1BAo6qB/X1FVDx7vjewWFTh WJdnGcpWMrjBUCXA6uZRlsvn9GDiqsx2aQUBei36QnsomYw5Tkn7eReZKzYRBBqAiMio 28nSXw8AAA1ZR4UNK+cIvnl6vyULYEDl+aXH6i5PXWoYQUWVMmPaBihHf1xePa1Oi5d7 EEBkFQwP3+5IP1oIPSavUTyIVt9Cw2hc7fEU/oB2pHE/16N0m2gLquja2i9e85OTKg7b LB0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1is8Iezkr6s4Ex2hsS25ZUz1zJxOesQz7FGVxmLzzqI=; b=Oxac0xnVPkizu5M5nyxtVaBRAu59zEEhRyWT7+E9GvVdyeO/e1xXjkCJh7hjZ1ayvZ e3EvNq1UWSl9REmqG/NCBfbXH/7no4C9zo8+JyeqnAhrzW6jdWkwHBAmn4uoEcvwvO/n pdF8sxes9iiWvjZqZdgiVK4KsKNe72CNucNo1fVKgI5vEXAqRXgyQy4PywgTernpjabm gbI5fAAnp3/iFuFKZxdUf/tUCylQPLwNQfOFaUc9KqKhxbcBFTK2wWTGJ81s8w/pbqBK 4vfh+DSgiHfYqT6GVAyG5PXNqiJmmCYnmSTJaAIiZeRSPaAUikzDqIY6qFg+6WZQzMXZ GD2A== X-Gm-Message-State: AOAM533MOOkR9u3Mxvz6F5NI+FDmwC78ZVUoGGwrjnqymZot0iJgwzOc 0XKNrTgY8maL2ZcnooOyX1kVsdWE61XPiAK1 X-Google-Smtp-Source: ABdhPJyns8437Q+5hM8XsgwJ283Nc3GlHAK7jJb/Oacs0upyz9HCdJ1ECJxstL3R70f5gzQstYvbDg== X-Received: by 2002:a63:cc53:0:b0:372:7d69:49fb with SMTP id q19-20020a63cc53000000b003727d6949fbmr19162683pgi.21.1650970521870; Tue, 26 Apr 2022 03:55:21 -0700 (PDT) Received: from localhost ([101.86.206.159]) by smtp.gmail.com with ESMTPSA id l2-20020a056a0016c200b004f7e3181a41sm15571637pfc.98.2022.04.26.03.55.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Apr 2022 03:55:21 -0700 (PDT) From: Patrick Wang To: paulmck@kernel.org, rostedt@goodmis.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, joel@joelfernandes.org, jiangshanlai@gmail.com Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, patrick.wang.shcn@gmail.com Subject: [PATCH v3] rcu: ftrace: avoid tracing a few functions executed in stop machine Date: Tue, 26 Apr 2022 18:55:11 +0800 Message-Id: <20220426105511.53010-1-patrick.wang.shcn@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Because of the change of stop machine implementation, there are functions being called while waiting currently: ---------------------------------------------------------------- Former stop machine wait loop: do { cpu_relax(); => macro ... } while (curstate != STOPMACHINE_EXIT); ----------------------------------------------------------------- Current stop machine wait loop: do { stop_machine_yield(cpumask); => function (notraced) ... touch_nmi_watchdog(); => function (notraced, inside calls also notraced) ... rcu_momentary_dyntick_idle(); => function (notraced, inside calls traced) } while (curstate != MULTI_STOP_EXIT); ------------------------------------------------------------------ These functions (including the calls inside) should be marked notrace to avoid their codes being updated when they are being called. The calls inside rcu_momentary_dyntick_idle() still remain traced, and will cause crash: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (0 ticks this GP) idle=14f/1/0x4000000000000000 softirq=3397/3397 fqs=0 rcu: 3-...!: (0 ticks this GP) idle=ee9/1/0x4000000000000000 softirq=5168/5168 fqs=0 (detected by 0, t=8137 jiffies, g=5889, q=2 ncpus=4) Task dump for CPU 1: task:migration/1 state:R running task stack: 0 pid: 19 ppid: 2 flags:0x00000000 Stopper: multi_cpu_stop+0x0/0x18c <- stop_machine_cpuslocked+0x128/0x174 Call Trace: Task dump for CPU 3: task:migration/3 state:R running task stack: 0 pid: 29 ppid: 2 flags:0x00000000 Stopper: multi_cpu_stop+0x0/0x18c <- stop_machine_cpuslocked+0x128/0x174 Call Trace: rcu: rcu_preempt kthread timer wakeup didn't happen for 8136 jiffies! g5889 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 rcu: Possible timer handling issue on cpu=2 timer-softirq=594 rcu: rcu_preempt kthread starved for 8137 jiffies! g5889 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:I stack: 0 pid: 14 ppid: 2 flags:0x00000000 Call Trace: schedule+0x56/0xc2 schedule_timeout+0x82/0x184 rcu_gp_fqs_loop+0x19a/0x318 rcu_gp_kthread+0x11a/0x140 kthread+0xee/0x118 ret_from_exception+0x0/0x14 rcu: Stack dump where RCU GP kthread last ran: Task dump for CPU 2: task:migration/2 state:R running task stack: 0 pid: 24 ppid: 2 flags:0x00000000 Stopper: multi_cpu_stop+0x0/0x18c <- stop_machine_cpuslocked+0x128/0x174 Call Trace: Mark the calls inside rcu_momentary_dyntick_idle(): rcu_preempt_deferred_qs() rcu_preempt_need_deferred_qs() rcu_preempt_deferred_qs_irqrestore() as notrace to prevent this. Signed-off-by: Patrick Wang --- v1->v2: - Modify log message. v2->v3: - Move "notrace" to behind "static" to keep the consistency with the rest of the code. kernel/rcu/tree_plugin.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c8ba0fe17267..440d9e02a26e 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -460,7 +460,7 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp) * be quite short, for example, in the case of the call from * rcu_read_unlock_special(). */ -static void +static notrace void rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) { bool empty_exp; @@ -581,7 +581,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) * is disabled. This function cannot be expected to understand these * nuances, so the caller must handle them. */ -static bool rcu_preempt_need_deferred_qs(struct task_struct *t) +static notrace bool rcu_preempt_need_deferred_qs(struct task_struct *t) { return (__this_cpu_read(rcu_data.cpu_no_qs.b.exp) || READ_ONCE(t->rcu_read_unlock_special.s)) && @@ -595,7 +595,7 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) * evaluate safety in terms of interrupt, softirq, and preemption * disabling. */ -static void rcu_preempt_deferred_qs(struct task_struct *t) +static notrace void rcu_preempt_deferred_qs(struct task_struct *t) { unsigned long flags; -- 2.25.1