From patchwork Mon Jul 31 23:16:37 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 128918 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:918b:0:b0:3e4:2afc:c1 with SMTP id s11csp2335310vqg; Mon, 31 Jul 2023 16:53:43 -0700 (PDT) X-Google-Smtp-Source: APBJJlFxsD0P414n4nUSpEsVmoemMU9LPNCzKEeML1+l22usfKRI0P6X1cCDqzSGY8/LxmD7uWpV X-Received: by 2002:a05:6a21:71cb:b0:133:bc8:8a47 with SMTP id ay11-20020a056a2171cb00b001330bc88a47mr11489857pzc.3.1690847622973; Mon, 31 Jul 2023 16:53:42 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1690847622; cv=none; d=google.com; s=arc-20160816; b=KqNvlxxGOsU7wdU3dmgvubQScJjAb/wwz4vgdVdeLOwFym7GE/ywTkbRL4YfG4DTNJ 76OC1MHcSLBBfgOJ8npLZksG9pnQb/TFcyQmWKot+s92giOnevo0xfccMVXtQx3EPHYb ST3inOFjdkS4STGLNZheaIpSs0Dyqf8O9WlJPHVmkpYjhG9I+vKOf6We/2Yt2WFL64h6 OAK/5QWwwd9NNEIH9nIeRe9wO8nARLdZIZlAqrSbPbWQIlXAksGopOxpUntMnrIVYwCD Tb6Mika+XjDoXm6rkZ5pjljWcVD9oIGHR0WyiLOcZBYyti7uxwm9EVOnB6pAeZPnP1J/ ppPA== 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=lruAlSV6huY6+IxUxQvlvNnzkm0AWvhiG/wzenI5Vgw=; fh=kgng34H5que7URbu24ZWqKKtWQj+H7d5uaZL8F1DzaU=; b=hW+MWU9uX5lGahqpJkNtSBrQgd9Z7tn9n9+GAv0PM9BfCXCKc3bGppjmMLdU1Sl7KF YjCYT0M2ZiZ83rj1hCZc5ZFJJGthASvcH998iKbXDGz2lOTDhCVkQHa4tmzSI6dDdCUr Lue393yKW5O2WJmPIYMXAyAOqMNf+6ESZJ3vpXZCgf4Qum+JhYUGfACcQ5cmPJvvCrly DCBS1JNrfilAKEcJg9djbYd1G8/k5wFSjSfcqxH0ZS5HSaXyEMG2PSNwl5WV0CZTN4YK tkA9EmMocz15OA8TpKraay/oZ91wpYRQp7t8XoW4kkdnFQemSVhzEjXMkvbV8iGwG4Or S9WA== 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 q6-20020a056a00088600b006687255a465si4038791pfj.298.2023.07.31.16.53.30; Mon, 31 Jul 2023 16:53:42 -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 S231909AbjGaXR0 (ORCPT + 99 others); Mon, 31 Jul 2023 19:17:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231866AbjGaXRQ (ORCPT ); Mon, 31 Jul 2023 19:17:16 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 135A91BEC for ; Mon, 31 Jul 2023 16:17:08 -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 5C14161356 for ; Mon, 31 Jul 2023 23:17:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C1F92C433CD; Mon, 31 Jul 2023 23:17:06 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.96) (envelope-from ) id 1qQc8P-003fLP-28; Mon, 31 Jul 2023 19:17:05 -0400 Message-ID: <20230731231705.484662632@goodmis.org> User-Agent: quilt/0.66 Date: Mon, 31 Jul 2023 19:16:37 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Andrew Morton Subject: [for-next][PATCH 03/15] tracing: Remove unnecessary copying of tr->current_trace References: <20230731231634.031452225@goodmis.org> MIME-Version: 1.0 X-Spam-Status: No, score=-6.7 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham 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: 1772982237237034104 X-GMAIL-MSGID: 1772982237237034104 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. Link: https://lkml.kernel.org/r/20230715141348.135792275@goodmis.org Cc: Mark Rutland Cc: Andrew Morton 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 f6ed6b79d91f..5e665c356df7 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4189,15 +4189,9 @@ 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 @@ -4846,16 +4840,8 @@ __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; @@ -4920,7 +4906,6 @@ __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: @@ -5005,7 +4990,6 @@ 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);