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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC569CDB474 for ; Mon, 23 Oct 2023 11:17:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230063AbjJWLR2 (ORCPT ); Mon, 23 Oct 2023 07:17:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233676AbjJWLR2 (ORCPT ); Mon, 23 Oct 2023 07:17:28 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98EDD92 for ; Mon, 23 Oct 2023 04:17:26 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6F87C433C9; Mon, 23 Oct 2023 11:17:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698059846; bh=bXYMbkfq65G3WKqjk6C02cJb/l3fJUSTcHvyXEnST6E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IvZHHfqIHwNXVqZRqyyt5I8y5/X8CG2YH+l5NS6ndGR0ZqcV0tC0R5dYLOu3b6+h2 gUPE0n6fVcGxir7Hf5WuoE/vvej2YLjICcETwoeP4F5UHXR069C9Xe3TqGa0nl2VNI t4XWIfiNaklYuZ9otHHsQ91K+LeGDkDwkVXqh44o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , Atish Patra , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 4.19 73/98] tracing: relax trace_event_eval_update() execution with cond_resched() Date: Mon, 23 Oct 2023 12:57:02 +0200 Message-ID: <20231023104816.150689783@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231023104813.580375891@linuxfoundation.org> References: <20231023104813.580375891@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Clément Léger [ Upstream commit 23cce5f25491968b23fb9c399bbfb25f13870cd9 ] When kernel is compiled without preemption, the eval_map_work_func() (which calls trace_event_eval_update()) will not be preempted up to its complete execution. This can actually cause a problem since if another CPU call stop_machine(), the call will have to wait for the eval_map_work_func() function to finish executing in the workqueue before being able to be scheduled. This problem was observe on a SMP system at boot time, when the CPU calling the initcalls executed clocksource_done_booting() which in the end calls stop_machine(). We observed a 1 second delay because one CPU was executing eval_map_work_func() and was not preempted by the stop_machine() task. Adding a call to cond_resched() in trace_event_eval_update() allows other tasks to be executed and thus continue working asynchronously like before without blocking any pending task at boot time. Link: https://lore.kernel.org/linux-trace-kernel/20230929191637.416931-1-cleger@rivosinc.com Cc: Masami Hiramatsu Signed-off-by: Clément Léger Tested-by: Atish Patra Reviewed-by: Atish Patra Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/trace_events.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index a3dc6c126b3ee..ed39d3ec202e6 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2242,6 +2242,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len) update_event_printk(call, map[i]); } } + cond_resched(); } up_write(&trace_event_sem); } -- 2.40.1