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 DA794C74A5B for ; Tue, 21 Mar 2023 15:11:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231475AbjCUPL1 (ORCPT ); Tue, 21 Mar 2023 11:11:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230472AbjCUPLW (ORCPT ); Tue, 21 Mar 2023 11:11:22 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A171E181; Tue, 21 Mar 2023 08:11:12 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679411470; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cBlQ00hG8MhlBw3zA8EtNC/Bw+Cu0Ips6JNpdNr1g4M=; b=fVwfxng4IJTFZtsvF5yprFb/Wp0n9ZX+YVtvS6VP0JX/6/0Vbv7GVCeL51O7ZtxD8le2kK 2Tvy1i/v6SNwo7OlIr0f9p2sENh4xSSCglMUubh8/o7+wEklup/srCZ9X/hjuYNd+x2d/c yWu2jxtyanfdUXDQPrhKakVWTRFix7dB57Ef73t7sPPC0hr3LBD0RXeKaYKomrVDK8Fpby gUZGXQw/uZ4mKgmMJVPVVBvq7y6C2x+BOyTFcD3P10v4iTCGLI2SiU4FFHBT9nOskH3hGT CheittC97+dYnkCxcBps8ffDush3p7q+UTCPTHNXeSUoo1/6QcVuctV0HbBo3A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679411470; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cBlQ00hG8MhlBw3zA8EtNC/Bw+Cu0Ips6JNpdNr1g4M=; b=2x5XtpYX4NC5EfkxM7kkgkx3ui432bSQnPyGkedfMh7q0Y4F4gh0SO76UXyaMeULraCzYY KDfMxDpKcyF2Y+BA== Date: Tue, 21 Mar 2023 16:11:07 +0100 MIME-Version: 1.0 Content-Language: en-US To: Steven Rostedt Cc: Donglin Peng , mhiramat@kernel.org, linux@armlinux.org.uk, mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, palmer@dabbelt.com, paul.walmsley@sifive.com, tglx@linutronix.de, dave.hansen@linux.intel.com, x86@kernel.org, mingo@redhat.com, xiehuan09@gmail.com, dinghui@sangfor.com.cn, huangcun@sangfor.com.cn, dolinux.peng@gmail.com, linux-trace-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20230320131650.482594-1-pengdonglin@sangfor.com.cn> <20230320131650.482594-2-pengdonglin@sangfor.com.cn> <2eeef5a3-cbe7-7a01-489a-87c5ac00adf7@linutronix.de> <20230321104413.43a81ffb@gandalf.local.home> From: Florian Kauer Subject: Re: [PATCH v5 1/2] function_graph: Support recording and printing the return value of function In-Reply-To: <20230321104413.43a81ffb@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21.03.23 15:44, Steven Rostedt wrote: > On Tue, 21 Mar 2023 15:09:40 +0100 > Florian Kauer wrote: > >> On 20.03.23 14:16, Donglin Peng wrote: >>> When using the function_graph tracer to analyze system call failures, >>> it can be time-consuming to analyze the trace logs and locate the kernel >>> function that first returns an error. This change aims to simplify the >>> process by recording the function return value to the 'retval' member of >>> 'ftrace_graph_ent' and printing it when outputing the trace log. >> >> I just came across your patch by pure luck and it helped me a lot >> to trace down a problem I had, thanks! >> >> So you can have my >> Tested-by: Florian Kauer >> >>> New trace options are introduced: funcgraph-retval and graph_retval_hex. >> >> I would personally prefer to have the second option scoped better, so for example >> "funcgraph-retval-hex". > > That could be an ftrace option. What do you mean? In the current implementation both funcgraph-retval and graph_retval_hex are options for the function_graph tracer, but one is prefixed with "funcgraph-" as nearly all other options for the function_graph tracer and one is not (and is even snake_case, while the others are kebab-case). So it just looks inconsistent for me, but there might be a reason? By the way: The documentation patch also references "function-retval" instead of "funcgraph-retval" in the documentation of the graph_retval_hex option. > Anyway, could you tell us your use case, and that could go into the change > log of this patch as "one use case that this helped with". Nothing spectacular. I just wanted to find out why ICMP port unreachable messages sporadically lead to -111 (Connection Refused) for __sys_sendto() when IP_RECVERR is set and the call never fails if IP_RECVERR is not set. (I am still unsure if this is REALLY intended behavior, but at least it makes sense why this occurs when reading the sources). And with this patch, the -111 is directly popping up in the trace, but I do not think that my missing knowledge about details of the kernel network stack really qualifies as a good argument ;-) Greetings, Florian