From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [217.70.183.201]) (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 3210718E06; Fri, 15 Mar 2024 18:03:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710525801; cv=none; b=Wv8FyzSz40K+Gq4lyvSceSOLWjzBgRr3ibOLDNnCQUdPsck7AQR94C0e9RKxPWGO5JhWMT9p0BICjGZCkxnyaKIrQDNruLBiog8kNekWrcnQRxdiG829jbtvLEeGo7th4NdrET/THu8DfwdfrbhYaf1h6KGoRuoiw1KLkTlpL70= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710525801; c=relaxed/simple; bh=96jjlzaKqPIoD+J27xsIk2R5l8th0S2N61/a556Lg3A=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=akFNe1iaGhuRJRohgFqykjCPqHgHOZvXoUujQRJpB3wzElr7wM206vwhNp1Py8tf7kAyKTZOeySnkqXoaBcuBVrAKr1Qu1NeAU+0YWS7Jaw8FqKKZn2k5yvSt/FSnroli9lqsUx6eXdzSzCAAA1k2v7LzYHpZbbfBTbnwnlQTeI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=IsdhNMIL; arc=none smtp.client-ip=217.70.183.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="IsdhNMIL" Received: by mail.gandi.net (Postfix) with ESMTPSA id 9DD251BF203; Fri, 15 Mar 2024 18:03:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1710525794; 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=VO5WZoCCq5NoqpHuTQPS36Qy1y1GqkTO5VES9r52zkQ=; b=IsdhNMILYndk7lAja94Rbuj9zEqXwi+IGFwPR1D66L3EaLl5481AdeJlUEPtRyBS/U+dOI R0HwG/6/Uyo+Js0//vR2akLv7SXUmK/JUcidrxpzqH7WauX2z2B/LCE5hKxiIBhJVCQELu X3CMrvdE+qU0WXjQLfLEHMlXTs52x0wTJ26+MTQ8xNl2c/khWYoWw26g7zNPdwBd/meSKe u4aJViL8tzt/WMcARqF0C/vkaFQxnhAcs0NjmUVXiclJXap7VrINnQc+m7h90+PNTRMIWP zJDbKW7eff1L3JHZ44cU8DCndTJedLZRWub2NTeeSJm5Ikt/JqH0UvEqezxh+w== Date: Fri, 15 Mar 2024 19:03:12 +0100 From: Luca Ceresoli To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Liam Girdwood , Mark Brown , Thomas Petazzoni Subject: Re: TP_printk() bug with %c, and more? Message-ID: <20240315190312.2bd6a198@booty> In-Reply-To: <20240315132146.29edf416@gandalf.local.home> References: <20240315174900.14418f22@booty> <20240315132146.29edf416@gandalf.local.home> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-GND-Sasl: luca.ceresoli@bootlin.com Hello Steven, thanks for the quick feedback! On Fri, 15 Mar 2024 13:21:46 -0400 Steven Rostedt wrote: > On Fri, 15 Mar 2024 17:49:00 +0100 > Luca Ceresoli wrote: > > > Hello Linux tracing maintainers, > > Hi Luca! > > > > > I've come across an unexpected behaviour in the kernel tracing > > infrastructure that looks like a bug, or maybe two. > > > > Cc-ing ASoC maintainers for as it appeared using ASoC traces, but it > > does not look ASoC-specific. > > > > It all started when using this trace-cmd sequence on an ARM64 board > > running a mainline 6.8.0-rc7 kernel: > > > > trace-cmd record -e snd_soc_dapm_path ./my-play > > trace-cmd report > > > > While this produces perfectly valid traces for other asoc events, > > the snd_soc_dapm_path produces: > > > > snd_soc_dapm_path: >c<* MIC1_EN <- (direct) <- > > > > instead of the expected: > > > > snd_soc_dapm_path: *MIC1 <- (direct) <- MIC1_EN > > > > The originating macro is: > > > > TP_printk("%c%s %s %s %s %s", > > (int) __entry->path_node && > > (int) __entry->path_connect ? '*' : ' ', > > __get_str(wname), DAPM_ARROW(__entry->path_dir), > > __get_str(pname), DAPM_ARROW(__entry->path_dir), > > __get_str(pnname)) > > > > It appears as if the %c placeholder always produces the three ">c<" > > characters, the '*' or ' ' char is printed as the first %s, all the > > other strings are shifted right by one position and the last string is > > never printed. > > > > On my x86_64 laptop running the default Ubuntu kernel (6.5) I'm able to > > trace a few events having a '%c' in their TP_printk() macros and the > > result is: > > > > intel_pipe_update_start: dev 0000:00:02.0, pipe >c<, frame=1, > > scanline=107856, min=2208, max=2154 > > > > What does /sys/kernel/tracing/trace show? It is correct: intel_pipe_update_start: dev 0000:00:02.0, pipe B, frame=377644, scanline=1466, min=2154, max=2159 > If that's fine, then the bug is in libtraceevent and not the kernel. > > I'm testing it out now, and I see %c not being processed properly by > libtraceevent. I'll take a deeper look. Thanks. > > originating from: > > > > TP_printk("dev %s, pipe %c, frame=%u, scanline=%u, min=%u, max=%u", > > > > Here it looks like the %c produced ">c<" again, but apparently without > > any shifting. > > > > Back on the ARM64 board I found a couple interesting clues. > > > > First, using the /tracing/ interface instead of trace-cmd, I'm > > getting correctly formatted strings: > > > > trace-cmd: snd_soc_dapm_path: >c<* HPOUT_L -> (direct) -> > > debugfs: snd_soc_dapm_path: *HPOUT_L <- (direct) <- HPOUT_POP_SOUND_L > > > > Notice the arrows pointing to the opposite direction though. The correct > > arrow is the one in the debugfs run. This other issue appears a separate bug however. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com