From patchwork Thu Jul 13 15:46:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 120011 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:a6b2:0:b0:3e4:2afc:c1 with SMTP id c18csp1944311vqm; Thu, 13 Jul 2023 09:33:19 -0700 (PDT) X-Google-Smtp-Source: APBJJlEltqv2F/XPO+E8Xw7agIa2/WGWQ8aKiE/H/RX9LYiJePTkOmj+APXDHokPkxRogqr2/nlW X-Received: by 2002:a05:6a20:1602:b0:133:449c:677c with SMTP id l2-20020a056a20160200b00133449c677cmr1700998pzj.58.1689265999423; Thu, 13 Jul 2023 09:33:19 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1689265999; cv=none; d=google.com; s=arc-20160816; b=a9jdayM4j3eqdHP43jAZGUhTnV1VMbyuuH8u71Ol8aDhne3YUMcgP+1guOsvxQH+IW TZwbONLRWyIR+Jv6btsmdAZsofEXairovpG/aSH20rG9wC30YS5Grl1Hol3nM/GkVElm dfFSV4qH8I9jqab6VhfGiDrCQjDzQrsMuChKPDwt0ol/49jgUjnNF7SrUA+VNlUDSXji 01D2f9ZJJjtOHTJw85KiSYfVSCQxvzikA5C48pWWWFruDkTok8RcxY/8/Y9kWO9zyio+ Q8mHL0eUgSY0AUts9Py6cNER6VpJF/Ak8IxFoJ0IIplXnBn5nCTluX1KglwKwv1232zD xhmw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date; bh=wXkQ5H6aj0/u8xlhT+hCA6kvQWbq1aI9F3Ie2xQ6JXU=; fh=YnVyIEcFvDD9bB9RjPWxIWHfBLuTviS9p0IMKoOVQMY=; b=k6R3cythW78uBghkJI8lGMn0iYW1Jhz6RBdjgV4aXAcUOctAUHYtGW8AlGbsnWaXTH oD9MKP9ElVECXQaDSs0r8AqnYXdKlN0/3I8G4yUZiQwByHHYlgmhU8/6rCAy3B2wbjHC uuIvLRO2rRntO07F8kMbnZY5AYMjbmjAdYMtvYhaXg7/mYRGsibi9ikSx7/LoFHJ4sOZ C8VEB5o/PIbOoXMn+nRGH1p7jx3DexEGu8McMgV3J7J6ZdLWhAaiwnM4nSe7cBtwGFNr KagsgutLNXlSLhFdAc04zqmPwTLgiAAPAoo5Sb6UPfEF8ztfT+4KUhxhqODN6RADfRO/ l49A== 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 x16-20020a056a00189000b006789229c538si5411467pfh.48.2023.07.13.09.33.06; Thu, 13 Jul 2023 09:33:19 -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 S232707AbjGMPqb (ORCPT + 99 others); Thu, 13 Jul 2023 11:46:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229691AbjGMPqa (ORCPT ); Thu, 13 Jul 2023 11:46:30 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45AD52686; Thu, 13 Jul 2023 08:46:29 -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 D59F661881; Thu, 13 Jul 2023 15:46:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB775C433C7; Thu, 13 Jul 2023 15:46:27 +0000 (UTC) Date: Thu, 13 Jul 2023 11:46:26 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mark Rutland , Zheng Yejian Subject: [PATCH 1/2] tracing: Remove unnecessary copying of tr->current_trace Message-ID: <20230713114626.704ebe8e@gandalf.local.home> In-Reply-To: <20230713114510.04c452ca@gandalf.local.home> References: <20230713114510.04c452ca@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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: 1771323784734327510 X-GMAIL-MSGID: 1771323784734327510 From: "Steven Rostedt (Google)" I have no idea why the iterator had to allocate a descriptor to make a copy of "current_trace" (now "tr->current_trace"). The content of that pointer never changes, so it's sufficient to just copy the pointer to maintain integrity with reading it. This is more of a clean up than a fix. Fixes: d7350c3f45694 ("tracing/core: make the read callbacks reentrants") Signed-off-by: Steven Rostedt (Google) Reviewed-by: Masami Hiramatsu (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);