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 87F1110E6 for ; Sun, 8 Oct 2023 00:51:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YLXsHeUm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 731F7C116AD; Sun, 8 Oct 2023 00:51:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696726265; bh=8D8u97XDPoWyNaB5aP1e19AHVlAsc8+LTpc7EvD2PFc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YLXsHeUm0QLB9a5oEg1YIk/BcExTt8EHZgZ5JXPyJ0Ilhxn4xr8NRCjlFfzCMWRn7 okPoXq63C9LqVUF5fHZ+3psvWR78ZDK9e0f5ukr7+SDAJjRkfVWUc3JMoeHR8ThRSC S7337kfc0w/hGM34HRtNxgz+zNXrVHUHiVWjrIWrmTL5tLRJGq63pGMCZiFcNDrhAx yCeXTz77JZMWFXXxx072uKMbHKVvrxDyUInbto+BEPZA/LEcJe1woOzM2PuluEjfFX yqQ2Wqv57HdCJTdI3aqpYpN5KAszRc+MAb+7vwcHngCFO1Qf/ZLWTmC1J6Dy+TeYiD h239kIMypJ12w== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , Masami Hiramatsu , Atish Patra , Steven Rostedt , Sasha Levin , linux-trace-kernel@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 7/7] tracing: relax trace_event_eval_update() execution with cond_resched() Date: Sat, 7 Oct 2023 20:50:53 -0400 Message-Id: <20231008005053.3768625-7-sashal@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231008005053.3768625-1-sashal@kernel.org> References: <20231008005053.3768625-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 4.14.326 Content-Transfer-Encoding: 8bit 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 37be6913cfb27..f29552b009c80 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2240,6 +2240,7 @@ 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