From patchwork Tue Feb 2 21:59:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 375969 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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 4950FC433E0 for ; Tue, 2 Feb 2021 22:02:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0326264F60 for ; Tue, 2 Feb 2021 22:02:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234387AbhBBWCE (ORCPT ); Tue, 2 Feb 2021 17:02:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:58600 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234197AbhBBWCC (ORCPT ); Tue, 2 Feb 2021 17:02:02 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2167664F60; Tue, 2 Feb 2021 22:01:22 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94) (envelope-from ) id 1l73jc-0096yN-Vn; Tue, 02 Feb 2021 17:01:20 -0500 Message-ID: <20210202220120.864689944@goodmis.org> User-Agent: quilt/0.66 Date: Tue, 02 Feb 2021 16:59:50 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , stable@vger.kernel.org, pierre.gondois@arm.com Subject: [for-linus][PATCH 1/5] fgraph: Initialize tracing_graph_pause at task creation References: <20210202215949.848582355@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Steven Rostedt (VMware)" On some archs, the idle task can call into cpu_suspend(). The cpu_suspend() will disable or pause function graph tracing, as there's some paths in bringing down the CPU that can have issues with its return address being modified. The task_struct structure has a "tracing_graph_pause" atomic counter, that when set to something other than zero, the function graph tracer will not modify the return address. The problem is that the tracing_graph_pause counter is initialized when the function graph tracer is enabled. This can corrupt the counter for the idle task if it is suspended in these architectures. CPU 1 CPU 2 ----- ----- do_idle() cpu_suspend() pause_graph_tracing() task_struct->tracing_graph_pause++ (0 -> 1) start_graph_tracing() for_each_online_cpu(cpu) { ftrace_graph_init_idle_task(cpu) task-struct->tracing_graph_pause = 0 (1 -> 0) unpause_graph_tracing() task_struct->tracing_graph_pause-- (0 -> -1) The above should have gone from 1 to zero, and enabled function graph tracing again. But instead, it is set to -1, which keeps it disabled. There's no reason that the field tracing_graph_pause on the task_struct can not be initialized at boot up. Cc: stable@vger.kernel.org Fixes: 380c4b1411ccd ("tracing/function-graph-tracer: append the tracing_graph_flag") Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211339 Reported-by: pierre.gondois@arm.com Signed-off-by: Steven Rostedt (VMware) --- init/init_task.c | 3 ++- kernel/trace/fgraph.c | 2 -- 2 files changed, 2 insertions(+), 3 deletions(-) diff --git a/init/init_task.c b/init/init_task.c index 8a992d73e6fb..3711cdaafed2 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -198,7 +198,8 @@ struct task_struct init_task .lockdep_recursion = 0, #endif #ifdef CONFIG_FUNCTION_GRAPH_TRACER - .ret_stack = NULL, + .ret_stack = NULL, + .tracing_graph_pause = ATOMIC_INIT(0), #endif #if defined(CONFIG_TRACING) && defined(CONFIG_PREEMPTION) .trace_recursion = 0, diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 73edb9e4f354..29a6ebeebc9e 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -394,7 +394,6 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } if (t->ret_stack == NULL) { - atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); t->curr_ret_stack = -1; t->curr_ret_depth = -1; @@ -489,7 +488,6 @@ static DEFINE_PER_CPU(struct ftrace_ret_stack *, idle_ret_stack); static void graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack) { - atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); t->ftrace_timestamp = 0; /* make curr_ret_stack visible before we add the ret_stack */