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 X-Spam-Level: X-Spam-Status: No, score=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E11CC43142 for ; Fri, 3 Aug 2018 02:34:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2F4021717 for ; Fri, 3 Aug 2018 02:34:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="wUTlYd+k" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2F4021717 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727374AbeHCE2a (ORCPT ); Fri, 3 Aug 2018 00:28:30 -0400 Received: from mail-qt0-f195.google.com ([209.85.216.195]:35351 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726305AbeHCE22 (ORCPT ); Fri, 3 Aug 2018 00:28:28 -0400 Received: by mail-qt0-f195.google.com with SMTP id a5-v6so4702510qtp.2 for ; Thu, 02 Aug 2018 19:34:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=J0vLw2pXtNo8xo2lrSjlBaA2pCmifQL71m7xlk33/Vk=; b=wUTlYd+kL/JbpkwQ33yjODCH0Sct5TgbNBYI1tEzwthYPiSElssQjxZxABrVipaETZ giK4EF3A2+G0oaAUJ4JOusaex9PgbEaWB/lP4Q3CUhCRvSUUKoADhL5kvlajUKk+QO17 b8wE9Sd+W7Sl9XcCz+Tu1WkdYB3IFrIRatPAQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=J0vLw2pXtNo8xo2lrSjlBaA2pCmifQL71m7xlk33/Vk=; b=soAOMbjZ3aZUiZv8w15zTRIi63rV/VrrlSMhjgsnWRPzz4pm1heCXfYL1Q0ZsEN6f/ QZxZHfDFbzprNNURTOklY5CohuxjaCEBTzdmHlpY3vyK5WK/QJiSEiBDIHMmrRmE5H1c q3acRB8NQEQCmYCbW+0cV+q6XnHmewAGoSBqMs3TEfwKIGmNTeSvKzxfYb0Lfn5gT5Vb T6y32kdrWdHkx0QXM7gWCdu/t1yAlW+tgRt588ntdMebm6PAruvn9vctyvSCSg/nQ3fH nCuHDxqXQwcC9SCgjH6H3/6+59xSxCK7VUfoX9SZjHLLtEQkSk1cRA8W739+KKMMfiSZ RJrA== X-Gm-Message-State: AOUpUlHpz7Nzi+x83PafuvCdqfOgYFeUsXIkO5uWNUnnm5eSNvoSKu06 6hr6Y++/DVd5OGEZy/Z0/s5KaP2wJzg= X-Google-Smtp-Source: AAOMgpccSqAUxlb0WcRam232dMvae9ThjwM6ICeeemGJ18/R4l60/HlpTwkiCB6jPntHGMixgzlZFg== X-Received: by 2002:ac8:2d61:: with SMTP id o30-v6mr2040637qta.253.1533263667083; Thu, 02 Aug 2018 19:34:27 -0700 (PDT) Received: from joelaf-glaptop0.roam.corp.google.com ([2600:1003:b86a:e60f:a119:1efd:28c9:65f7]) by smtp.gmail.com with ESMTPSA id t34-v6sm3206934qtt.81.2018.08.02.19.34.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 Aug 2018 19:34:26 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, "Joel Fernandes (Google)" , Ingo Molnar , Steven Rostedt , mathieu.desnoyers@efficios.com, mhiramat@kernel.org, paulmck@linux.vnet.ibm.com, peterz@infradead.org Subject: [PATCH] trace: Use rcu_dereference_raw for hooks from trace-event subsystem Date: Thu, 2 Aug 2018 19:34:07 -0700 Message-Id: <20180803023407.225852-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.18.0.597.ga71716f1ad-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since we switched to using SRCU for tracepoints used in the idle path, we can no longer use rcu_dereference_sched for dereferencing points in trace-event hooks. Since tracepoints can now use either SRCU or sched-RCU, just use rcu_dereference_raw for traceevents just like we're doing when dereferencing the tracepoint table. This prevents an RCU warning reported by Masami: [ 282.060593] WARNING: can't dereference registers at 00000000f3c7f62b [ 282.063200] ============================= [ 282.064082] WARNING: suspicious RCU usage [ 282.064963] 4.18.0-rc6+ #15 Tainted: G W [ 282.066048] ----------------------------- [ 282.066923] /home/mhiramat/ksrc/linux/kernel/trace/trace_events.c:242 suspicious rcu_dereference_check() usage! [ 282.068974] [ 282.068974] other info that might help us debug this: [ 282.068974] [ 282.070770] [ 282.070770] RCU used illegally from idle CPU! [ 282.070770] rcu_scheduler_active = 2, debug_locks = 1 [ 282.072938] RCU used illegally from extended quiescent state! [ 282.074183] no locks held by swapper/0/0. [ 282.075071] [ 282.075071] stack backtrace: [ 282.076121] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W [ 282.077782] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) [ 282.079604] Call Trace: [ 282.080212] [ 282.080755] dump_stack+0x85/0xcb [ 282.081523] trace_event_ignore_this_pid+0x66/0x70 [ 282.082541] trace_event_raw_event_preemptirq_template+0xa2/0xb0 [ 282.083774] ? interrupt_entry+0xc4/0xe0 [ 282.084665] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 282.085669] trace_hardirqs_off_caller+0x90/0xd0 [ 282.086597] trace_hardirqs_off_thunk+0x1a/0x1c [ 282.087433] ? call_function_interrupt+0xa/0x20 [ 282.088201] interrupt_entry+0xc4/0xe0 [ 282.088848] ? call_function_interrupt+0xa/0x20 [ 282.089579] [ 282.090029] ? native_safe_halt+0x2/0x10 [ 282.090695] ? default_idle+0x1f/0x160 [ 282.091330] ? default_idle_call+0x24/0x40 [ 282.091997] ? do_idle+0x210/0x250 [ 282.092658] ? cpu_startup_entry+0x6f/0x80 [ 282.093338] ? start_kernel+0x49d/0x4bd [ 282.093987] ? secondary_startup_64+0xa5/0xb0 Reported-by: Masami Hiramatsu Fixes: e6753f23d961 ("tracepoint: Make rcuidle tracepoint callers use SRCU") Signed-off-by: Joel Fernandes (Google) --- kernel/trace/trace_events.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 14ff4ff3caab..7b508ce8ac44 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -239,7 +239,7 @@ bool trace_event_ignore_this_pid(struct trace_event_file *trace_file) struct trace_array_cpu *data; struct trace_pid_list *pid_list; - pid_list = rcu_dereference_sched(tr->filtered_pids); + pid_list = rcu_dereference_raw(tr->filtered_pids); if (!pid_list) return false; @@ -512,7 +512,7 @@ event_filter_pid_sched_process_exit(void *data, struct task_struct *task) struct trace_pid_list *pid_list; struct trace_array *tr = data; - pid_list = rcu_dereference_sched(tr->filtered_pids); + pid_list = rcu_dereference_raw(tr->filtered_pids); trace_filter_add_remove_task(pid_list, NULL, task); } -- 2.18.0.597.ga71716f1ad-goog