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 X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A770C5CFEB for ; Wed, 11 Jul 2018 05:26:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4732F20883 for ; Wed, 11 Jul 2018 05:26:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="Oyp8j6QF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4732F20883 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726597AbeGKF3Y (ORCPT ); Wed, 11 Jul 2018 01:29:24 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:45494 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726223AbeGKF3Y (ORCPT ); Wed, 11 Jul 2018 01:29:24 -0400 Received: by mail-pf0-f195.google.com with SMTP id i26-v6so6205198pfo.12 for ; Tue, 10 Jul 2018 22:26:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=a3RsdqZG/dqfLp6B1pjuDa90GE/UllS5m83ONEvDULI=; b=Oyp8j6QFyRQ25/uko5m2ktfDpGPgqVP91UYFGa9Tggl2XJCdTq7eN60SdrKyYz5Ojc +4JDzZNkk6+UiQN/JoelFsLDoVTVfRZPasTyR0ybPyzCPYc52xPX3eImZOgTRcEBMMtH lAEBjlMiUsUBPoDdC7NhVJztavE5c54Sq8R70= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=a3RsdqZG/dqfLp6B1pjuDa90GE/UllS5m83ONEvDULI=; b=jftxrVMTNcn5k0bU1PiPuGNIq7mh7r+lWtA4uD6ROnmFptKqZNuHoG1Rc5Mh02MNzD n5axH8Rm0LgnQThJXMftT6L+rRJDx4WnIChNUZ+o7S+quFRVcG3xB2Kty2+xWBVNi61l 5VuAT//850LpQK89g7z7nzS8kduAxtSpATsnNkt9l0n9SotflHlE6AOCgbfNd4nYUmpg EHZiOaNsIhFMzoitzQjJA8+YniD/V4Apdd4z9vIVkzATjtC5c5smLNNXo/alZR/u5SNw 6VAIeFwUPAGnKV0UpwAXGzSltu5FUTvT7mJJkws9iD+eR5TnvcLI9Ozbirlsy9R+kRG5 zneg== X-Gm-Message-State: APt69E3aPPUpLm2/9lGvbmnLQTL+4wV+sc/oFGJFnfKr+ACH5jwDF6pU OnuNhanGWu/JJF7jtcV3TqNqAg== X-Google-Smtp-Source: AAOMgpfY1gupw4iOm/thYcJ8kAtNPAbUw41RQ+SPD8UO5IebNPUOXlAg8MORg5MG6YSSSOtx3UNgLA== X-Received: by 2002:a63:2c8e:: with SMTP id s136-v6mr17026051pgs.390.1531286814090; Tue, 10 Jul 2018 22:26:54 -0700 (PDT) Received: from localhost ([2620:0:1000:1600:3122:ea9c:d178:eb]) by smtp.gmail.com with ESMTPSA id 65-v6sm27058873pfq.81.2018.07.10.22.26.53 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 10 Jul 2018 22:26:53 -0700 (PDT) Date: Tue, 10 Jul 2018 22:26:52 -0700 From: Joel Fernandes To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Andy Shevchenko , Boqun Feng , Byungchul Park , Ingo Molnar , Julia Cartwright , linux-kselftest@vger.kernel.org, Masami Hiramatsu , Mathieu Desnoyers , kernel-team@android.com, Namhyung Kim , Paul McKenney , Peter Zijlstra , Thomas Glexiner , Tom Zanussi Subject: Re: [PATCH v9 6/7] lib: Add module to simulate atomic sections for testing preemptoff tracers Message-ID: <20180711052652.GA11372@joelaf.mtv.corp.google.com> References: <20180628182149.226164-1-joel@joelfernandes.org> <20180628182149.226164-7-joel@joelfernandes.org> <20180710204707.2fbaef87@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180710204707.2fbaef87@gandalf.local.home> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 10, 2018 at 08:47:07PM -0400, Steven Rostedt wrote: > On Thu, 28 Jun 2018 11:21:48 -0700 > Joel Fernandes wrote: > > > From: "Joel Fernandes (Google)" > > > > In this patch we introduce a test module for simulating a long atomic > > section in the kernel which the preemptoff or irqsoff tracers can > > detect. This module is to be used only for test purposes and is default > > disabled. > > > > Following is the expected output (only briefly shown) that can be parsed > > to verify that the tracers are working correctly. We will use this from > > the kselftests in future patches. > > > > For the preemptoff tracer: > > > > echo preemptoff > /d/tracing/current_tracer > > sleep 1 > > insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000 > > sleep 1 > > bash-4.3# cat /d/tracing/trace > > preempt -1066 2...2 0us@: atomic_sect_run <-atomic_sect_run > > preempt -1066 2...2 500002us : atomic_sect_run <-atomic_sect_run > > preempt -1066 2...2 500004us : tracer_preempt_on <-atomic_sect_run > > preempt -1066 2...2 500012us : > > => kthread > > => ret_from_fork > > > > For the irqsoff tracer: > > > > echo irqsoff > /d/tracing/current_tracer > > sleep 1 > > insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000 > > sleep 1 > > bash-4.3# cat /d/tracing/trace > > irq dis -1069 1d..1 0us@: atomic_sect_run > > irq dis -1069 1d..1 500001us : atomic_sect_run > > irq dis -1069 1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run > > irq dis -1069 1d..1 500005us : > > => ret_from_fork > > > > Co-developed-by: Erick Reyes > > Cc: Andy Shevchenko > > Reviewed-by: Andy Shevchenko > > Signed-off-by: Joel Fernandes (Google) > > --- > > lib/Kconfig.debug | 8 ++++ > > lib/Makefile | 1 + > > lib/test_atomic_sections.c | 77 ++++++++++++++++++++++++++++++++++++++ > > I think this code should reside in kernel/trace directory. I already > have modules there. See the ring_buffer_benchmark code and the test > module for mmio tracer. Ok, I'll move it to there. > > 3 files changed, 86 insertions(+) > > create mode 100644 lib/test_atomic_sections.c > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index 8838d1158d19..622c90e1e066 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -1956,6 +1956,14 @@ config TEST_KMOD > > > > If unsure, say N. > > > > +config TEST_ATOMIC_SECTIONS > > + tristate "Simulate atomic sections for tracers to detect" > > Hmm, I don't like this title. It's not very obvious to what it is > about. What about "Preempt / IRQ disable delay thread to test latency > tracers" ? Or something along those lines. Sure, I'll change it to that. I agree its better. I'll change the text to that and call the config TEST_PREEMPT_IRQ_DISABLE_DELAY. > > + depends on m > > + help > > + Select this option to build a test module that can help test atomic > > + sections by simulating them with a duration supplied as a module > > + parameter. Preempt disable and irq disable modes can be requested. > > "If unsure say N" Sure, sounds good. > > + > > config TEST_DEBUG_VIRTUAL > > tristate "Test CONFIG_DEBUG_VIRTUAL feature" > > depends on DEBUG_VIRTUAL > > diff --git a/lib/Makefile b/lib/Makefile > > index 90dc5520b784..7831e747bf72 100644 > > --- a/lib/Makefile > > +++ b/lib/Makefile > > @@ -44,6 +44,7 @@ obj-y += string_helpers.o > > obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o > > obj-y += hexdump.o > > obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o > > +obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o > > obj-y += kstrtox.o > > obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o > > obj-$(CONFIG_TEST_BPF) += test_bpf.o > > diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c > > new file mode 100644 > > index 000000000000..1eef518f0974 > > --- /dev/null > > +++ b/lib/test_atomic_sections.c > > @@ -0,0 +1,77 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Atomic section emulation test module > > + * > > + * Emulates atomic sections by disabling IRQs or preemption > > + * and doing a busy wait for a specified amount of time. > > + * This can be used for testing of different atomic section > > + * tracers such as irqsoff tracers. > > + * > > + * (c) 2018. Google LLC > > + */ > > + > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +static ulong atomic_time = 100; > > +static char atomic_mode[10] = "irq"; > > + > > +module_param_named(atomic_time, atomic_time, ulong, S_IRUGO); > > +module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO); > > +MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)"); > > It's not a "Period", it's a delay. "Length of time in critical section" Sure. > > +MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)"); > > "Mode of the test: preempt or irq disabled (default irq)" Ok. > > + > > +static void busy_wait(ulong time) > > +{ > > + ktime_t start, end; > > + start = ktime_get(); > > + do { > > + end = ktime_get(); > > + if (kthread_should_stop()) > > + break; > > + } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); > > +} > > + > > +int atomic_sect_run(void *data) > > +{ > > + unsigned long flags; > > + > > + if (!strcmp(atomic_mode, "irq")) { > > + local_irq_save(flags); > > + busy_wait(atomic_time); > > + local_irq_restore(flags); > > + } else if (!strcmp(atomic_mode, "preempt")) { > > + preempt_disable(); > > + busy_wait(atomic_time); > > + preempt_enable(); > > + } > > So this is a one shot deal? That should be explained somewhere, > probably in the config help message. In fact, I think the config help > message should show how to use this. Sounds good, I'll clarify it better. Thanks! - Joel