From patchwork Sat Jul 15 14:12:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 120797 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:c923:0:b0:3e4:2afc:c1 with SMTP id j3csp198102vqt; Sat, 15 Jul 2023 07:30:21 -0700 (PDT) X-Google-Smtp-Source: APBJJlEDDShK5xeBp9/adwJUCmbLObBGZ1d3mBddKWtpZz5hpDpJpDx59cneD97XOLoeuR/RdLzg X-Received: by 2002:a17:906:109:b0:992:ef60:aadd with SMTP id 9-20020a170906010900b00992ef60aaddmr7748848eje.13.1689431421379; Sat, 15 Jul 2023 07:30:21 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1689431421; cv=none; d=google.com; s=arc-20160816; b=n5bpNs1rfsT1QmlM1XAPgRW0o017vjZByNhuM+fHIyIjmhv+KoKeds2W4gJFHnXnbv bm6SIrcCj6LcMzRZm8f2R6kdUkcTWMnpQqIYqsXCtMAKn4JCgHtILNr5KjNgWBhnYkZV a4Mhr1WnbFKQ2fvuOOyCYmVumaQzGleSCEuEh57ZbA46lwnHerVVNUopHJ5M1JGF4r4M tZ7Wa54RPcPg51vx2IRUz/Ej0+2rel/dR5WOsF3F2bq8UMfTJfKLvhd5HmsbttB9VsfD ufQUGuFDYNZ/l625S33P9XrzAGcA/FVjdISOXfu57sx27bb4EsUACpuLEKAaYXNz1nf1 H33A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:mime-version:references:subject:cc:to:from:date :user-agent:message-id; bh=eSp8Gblajkl4yDXBITVRPJ0OXA9MWnz5iau14bdVnlU=; fh=ST8jSSvP817CUTShQq7KX/jX436RioQu2dYbRCsWhEU=; b=CtTHxf/iOdOHTuqfHcDrdykb2ucQbAA022vYU9JuayN+Jhc9OI9cVe4mZFnlZGQ8ib 3qBfIpi40L3t3mt4bfzvMukTTvPQq7VI2G1lrJc/GbpR3ehRRxwFelpxlk6vSHbIbEq2 nD2E8BdshDnveul+u0IBxEpZYo6tgcWtOOVJwdgVMtPsyTs09058hyFwyi14CK4HPWAb DKN676YfANKK54LWv1rtnrlwt7XtkerA6XbqmLxnNGNiq54qnuD8IrY9hCgO884QdWBy HvmCL8MdwN7YTvjh7vx5vDnf5vB+eIqG2XbkRHBpMV83StxfzHKAvMLkvywPZsK+o5nR 3lfw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id lv9-20020a170906bc8900b0099295afb9cdsi10701609ejb.419.2023.07.15.07.29.56; Sat, 15 Jul 2023 07:30:21 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230056AbjGOON5 (ORCPT + 99 others); Sat, 15 Jul 2023 10:13:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229967AbjGOONv (ORCPT ); Sat, 15 Jul 2023 10:13:51 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 559E81BD4; Sat, 15 Jul 2023 07:13:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E8DFF60BB8; Sat, 15 Jul 2023 14:13:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59555C433C7; Sat, 15 Jul 2023 14:13:49 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.96) (envelope-from ) id 1qKg1s-00103S-12; Sat, 15 Jul 2023 10:13:48 -0400 Message-ID: <20230715141348.135792275@goodmis.org> User-Agent: quilt/0.66 Date: Sat, 15 Jul 2023 10:12:14 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Andrew Morton Subject: [PATCH v2 1/2] tracing: Remove unnecessary copying of tr->current_trace References: <20230715141213.970003974@goodmis.org> MIME-Version: 1.0 X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1771497241646924246 X-GMAIL-MSGID: 1771497241646924246 From: "Steven Rostedt (Google)" The iterator allocated a descriptor to copy the current_trace. This was done with the assumption that the function pointers might change. But this was a false assuption, as it does not change. There's no reason to make a copy of the current_trace and just use the pointer it points to. This removes needing to manage freeing the descriptor. Worse yet, there's locations that the iterator is used but does make a copy and just uses the pointer. This could cause the actual pointer to the trace descriptor to be freed and not the allocated copy. This is more of a clean up than a fix. Fixes: d7350c3f45694 ("tracing/core: make the read callbacks reentrants") Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index be847d45d81c..1c370ffbe062 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4205,15 +4205,9 @@ static void *s_start(struct seq_file *m, loff_t *pos) loff_t l = 0; int cpu; - /* - * copy the tracer to avoid using a global lock all around. - * iter->trace is a copy of current_trace, the pointer to the - * name may be used instead of a strcmp(), as iter->trace->name - * will point to the same string as current_trace->name. - */ mutex_lock(&trace_types_lock); - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) - *iter->trace = *tr->current_trace; + if (unlikely(tr->current_trace != iter->trace)) + iter->trace = tr->current_trace; mutex_unlock(&trace_types_lock); #ifdef CONFIG_TRACER_MAX_TRACE @@ -4862,16 +4856,8 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) iter->fmt = NULL; iter->fmt_size = 0; - /* - * We make a copy of the current tracer to avoid concurrent - * changes on it while we are reading. - */ mutex_lock(&trace_types_lock); - iter->trace = kzalloc(sizeof(*iter->trace), GFP_KERNEL); - if (!iter->trace) - goto fail; - - *iter->trace = *tr->current_trace; + iter->trace = tr->current_trace; if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL)) goto fail; @@ -4936,7 +4922,6 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) fail: mutex_unlock(&trace_types_lock); - kfree(iter->trace); kfree(iter->temp); kfree(iter->buffer_iter); release: @@ -5021,7 +5006,6 @@ static int tracing_release(struct inode *inode, struct file *file) free_cpumask_var(iter->started); kfree(iter->fmt); kfree(iter->temp); - kfree(iter->trace); kfree(iter->buffer_iter); seq_release_private(inode, file);