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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C0DBC433F5 for ; Tue, 28 Sep 2021 03:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4776361262 for ; Tue, 28 Sep 2021 03:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238816AbhI1DOG (ORCPT ); Mon, 27 Sep 2021 23:14:06 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:55836 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238748AbhI1DOF (ORCPT ); Mon, 27 Sep 2021 23:14:05 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R461e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=yun.wang@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UptRZmW_1632798744; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0UptRZmW_1632798744) by smtp.aliyun-inc.com(127.0.0.1); Tue, 28 Sep 2021 11:12:25 +0800 To: Steven Rostedt , Ingo Molnar , open list From: =?UTF-8?B?546L6LSH?= Subject: [RESEND PATCH v2] trace: prevent preemption in perf_ftrace_function_call() Message-ID: Date: Tue, 28 Sep 2021 11:12:24 +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 telling us the CPU could be changed after task is preempted, and the checking on CPU before preemption will be invalid. This patch just turn off preemption in perf_ftrace_function_call() to prevent CPU changing. Reported-by: Abaci Signed-off-by: Michael Wang --- kernel/trace/trace_event_perf.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 6aed10e..dcbefdf 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -441,12 +441,19 @@ void perf_trace_buf_update(void *record, u16 type) if (!rcu_is_watching()) return; + /* + * Prevent CPU changing from now on. rcu must + * be in watching if the task was migrated and + * scheduled. + */ + preempt_disable_notrace(); + 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 +475,18 @@ void perf_trace_buf_update(void *record, u16 type) entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); if (!entry) - goto out; + goto unlock; entry->ip = ip; entry->parent_ip = parent_ip; perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 1, ®s, &head, NULL); -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