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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 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 32353C433EF for ; Thu, 23 Sep 2021 03:45:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1506760F4C for ; Thu, 23 Sep 2021 03:45:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239670AbhIWDrD (ORCPT ); Wed, 22 Sep 2021 23:47:03 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:42052 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239285AbhIWDoa (ORCPT ); Wed, 22 Sep 2021 23:44:30 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R701e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=yun.wang@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UpHnR.b_1632368577; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0UpHnR.b_1632368577) by smtp.aliyun-inc.com(127.0.0.1); Thu, 23 Sep 2021 11:42:57 +0800 To: Steven Rostedt , Ingo Molnar , open list From: =?UTF-8?B?546L6LSH?= Subject: [RFC PATCH] trace: prevent preemption in perf_ftrace_function_call() Message-ID: <2470f39b-aed1-4e19-9982-206007eb0c6a@linux.alibaba.com> Date: Thu, 23 Sep 2021 11:42:56 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With CONFIG_DEBUG_PREEMPT we observed reports like: BUG: using smp_processor_id() in preemptible caller is perf_ftrace_function_call+0x6f/0x2e0 CPU: 1 PID: 680 Comm: a.out Not tainted Call Trace: dump_stack_lvl+0x8d/0xcf check_preemption_disabled+0x104/0x110 ? optimize_nops.isra.7+0x230/0x230 ? text_poke_bp_batch+0x9f/0x310 perf_ftrace_function_call+0x6f/0x2e0 ... __text_poke+0x5/0x620 text_poke_bp_batch+0x9f/0x310 This tell us the CPU could be changed after task is preempted, and the checking on CPU before preemption is helpless. This patch just turn off preemption in perf_ftrace_function_call() to prevent CPU changing. Signed-off-by: Michael Wang --- kernel/trace/trace_event_perf.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 6aed10e..5486b18 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -438,15 +438,17 @@ void perf_trace_buf_update(void *record, u16 type) int rctx; int bit; + preempt_disable_notrace(); + if (!rcu_is_watching()) - return; + goto out; if ((unsigned long)ops->private != smp_processor_id()) - return; + goto out; bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) - return; + goto out; event = container_of(ops, struct perf_event, ftrace_ops); @@ -468,16 +470,18 @@ void perf_trace_buf_update(void *record, u16 type) entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); if (!entry) - goto out; + goto out_unlock; entry->ip = ip; entry->parent_ip = parent_ip; perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 1, ®s, &head, NULL); -out: +out_unlock: ftrace_test_recursion_unlock(bit); #undef ENTRY_SIZE +out: + preempt_enable_notrace(); } static int perf_ftrace_function_register(struct perf_event *event) -- 1.8.3.1