From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E6D21116 for ; Mon, 23 Oct 2023 11:07:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Q44Fnta9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92A0DC433C7; Mon, 23 Oct 2023 11:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698059242; bh=l7AlLrM7KU1bojVgWnBIFT4IbsLgYbmpkcA3KpQMu1s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q44Fnta9VM3JtRhEs3DG9bkP3rlg9uK9kQQzxSK4nQj7GZZVNzXUSfxWmecrNsXFU 1gg7ERN0TyBU4YXHd/kuGKylHUkZX7VL8lJDnk527IuU4I0MneSgcpJnnsSOrRThQ7 pUN/8kRgPWIbQfeR2PhPzfbzCK96b2JJ3lgkPC6U= 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 6.5 111/241] tracing: relax trace_event_eval_update() execution with cond_resched() Date: Mon, 23 Oct 2023 12:54:57 +0200 Message-ID: <20231023104836.597480999@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231023104833.832874523@linuxfoundation.org> References: <20231023104833.832874523@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.5-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 0cf84a7449f5b..9841589b4af7f 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2777,6 +2777,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len) update_event_fields(call, map[i]); } } + cond_resched(); } up_write(&trace_event_sem); } -- 2.40.1