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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 64739C4360C for ; Tue, 8 Oct 2019 22:08:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F13721835 for ; Tue, 8 Oct 2019 22:08:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SYvESW+0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727474AbfJHWIj (ORCPT ); Tue, 8 Oct 2019 18:08:39 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:36954 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727051AbfJHWIg (ORCPT ); Tue, 8 Oct 2019 18:08:36 -0400 Received: by mail-qt1-f194.google.com with SMTP id l51so220676qtc.4 for ; Tue, 08 Oct 2019 15:08:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=YLk4rgpI3ra8cq7GidJOjYQl2q+Qi2SppaV+ZdIOjAo=; b=SYvESW+006swsiAsiQLllk9UC06MtAXhBLb+Ahx9TWFv1pB/FASQNcRlMtcHkL3KiB 87uOm87O7OlfDBDgMJfHdni905RIE90TUAj5ux8ltdAzSZxmPuWk/LKqUMFYj4tEFnIb DOOw/UT0T9luV5EkWxRtZdCWsyGpHXM4nxpECUpZCulMm19a4C7pE9TDSORFoQIZvYwF Gv6qXXNZVp/S1ufh4OkLeNEYgpHELNiaZ9qaVQcfA52DAOwnAwDiwRmbXZOasyvNDYok R5NhxhcUTH5oU1Vi1k4jG8fGXlw4Av/M261N2Um8Ne1F8DSI4rdXnpmvyUB0KxdOCZl6 yr0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=YLk4rgpI3ra8cq7GidJOjYQl2q+Qi2SppaV+ZdIOjAo=; b=qyNOxtgztESbfnWWxSE+c20PgYiiA1qjwK5wdAWW0ipCEeqLVsIr+JsFPCzPmDp88z z/ODmcz2scpQ1ufo1L0onPh9gRQjWqflpz6ANAf5JxSeP2IYc/UO9QUVLoOs9jAQ48vu vwZ+6teGVzG5laTnzJnyS2oOGC4zmKzRkNP83oGp/YLcap7AOBTK72TMg7v0o5V66FHS 6cARiivBRIH5ZN5UQd7y9NjThzbH3oG/KO3xOSYMLRSRP+HW8IdCHKLJRoYeQUnwM5el 8G269D/HHK6fPiSoBwpy8SZUPB8XvKQt0JFTIyh6e3UkejmWC4t9+cwmfTNxKpyZyH0b gOow== X-Gm-Message-State: APjAAAXRM/DBl3J8YOlup8WS0FLkAPshNbkaK8j3wzJcj8PWs/Z6YEFu TypFWXNmAIo7AQXuUTtd7Q== X-Google-Smtp-Source: APXvYqwIxrT2r9Vm6ix2N/F7sKQ0XwYBAWdv4gTcvGEMbRpFiDMK8fFwaegcTFMKlqH9MqWqsyllVQ== X-Received: by 2002:ad4:43e9:: with SMTP id f9mr474167qvu.66.1570572515336; Tue, 08 Oct 2019 15:08:35 -0700 (PDT) Received: from localhost.localdomain ([92.117.168.143]) by smtp.gmail.com with ESMTPSA id m19sm42346qke.22.2019.10.08.15.08.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Oct 2019 15:08:34 -0700 (PDT) From: "Viktor Rosendahl (BMW)" To: Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org Cc: Joel Fernandes , "Viktor Rosendahl (BMW)" Subject: [PATCH v8 2/4] preemptirq_delay_test: Add the burst feature and a sysfs trigger Date: Wed, 9 Oct 2019 00:08:22 +0200 Message-Id: <20191008220824.7911-3-viktor.rosendahl@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191008220824.7911-1-viktor.rosendahl@gmail.com> References: <20191008220824.7911-1-viktor.rosendahl@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This burst feature enables the user to generate a burst of preempt/irqsoff latencies. This makes it possible to test whether we are able to detect latencies that systematically occur very close to each other. The maximum burst size is 10. We also create 10 identical test functions, so that we get 10 different backtraces; this is useful when we want to test whether we can detect all the latencies in a burst. Otherwise, there would be no easy way of differentiating between which latency in a burst was captured by the tracer. In addition, there is a sysfs trigger, so that it's not necessary to reload the module to repeat the test. The trigger will appear as /sys/kernel/preemptirq_delay_test/trigger in sysfs. Signed-off-by: Viktor Rosendahl (BMW) Reviewed-by: Joel Fernandes (Google) --- kernel/trace/Kconfig | 6 +- kernel/trace/preemptirq_delay_test.c | 144 +++++++++++++++++++++++---- 2 files changed, 128 insertions(+), 22 deletions(-) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e08527f50d2a..2a58380ea310 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -752,9 +752,9 @@ config PREEMPTIRQ_DELAY_TEST configurable delay. The module busy waits for the duration of the critical section. - For example, the following invocation forces a one-time irq-disabled - critical section for 500us: - modprobe preemptirq_delay_test test_mode=irq delay=500000 + For example, the following invocation generates a burst of three + irq-disabled critical sections for 500us: + modprobe preemptirq_delay_test test_mode=irq delay=500 burst_size=3 If unsure, say N diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c index d8765c952fab..31c0fad4cb9e 100644 --- a/kernel/trace/preemptirq_delay_test.c +++ b/kernel/trace/preemptirq_delay_test.c @@ -10,18 +10,25 @@ #include #include #include +#include #include #include #include #include +#include static ulong delay = 100; -static char test_mode[10] = "irq"; +static char test_mode[12] = "irq"; +static uint burst_size = 1; -module_param_named(delay, delay, ulong, S_IRUGO); -module_param_string(test_mode, test_mode, 10, S_IRUGO); -MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)"); -MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)"); +module_param_named(delay, delay, ulong, 0444); +module_param_string(test_mode, test_mode, 12, 0444); +module_param_named(burst_size, burst_size, uint, 0444); +MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)"); +MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)"); +MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)"); + +#define MIN(x, y) ((x) < (y) ? (x) : (y)) static void busy_wait(ulong time) { @@ -34,37 +41,136 @@ static void busy_wait(ulong time) } while ((end - start) < (time * 1000)); } -static int preemptirq_delay_run(void *data) +static __always_inline void irqoff_test(void) { unsigned long flags; + local_irq_save(flags); + busy_wait(delay); + local_irq_restore(flags); +} - if (!strcmp(test_mode, "irq")) { - local_irq_save(flags); - busy_wait(delay); - local_irq_restore(flags); - } else if (!strcmp(test_mode, "preempt")) { - preempt_disable(); - busy_wait(delay); - preempt_enable(); +static __always_inline void preemptoff_test(void) +{ + preempt_disable(); + busy_wait(delay); + preempt_enable(); +} + +static void execute_preemptirqtest(int idx) +{ + if (!strcmp(test_mode, "irq")) + irqoff_test(); + else if (!strcmp(test_mode, "preempt")) + preemptoff_test(); + else if (!strcmp(test_mode, "alternate")) { + if (idx % 2 == 0) + irqoff_test(); + else + preemptoff_test(); } +} + +#define DECLARE_TESTFN(POSTFIX) \ + static void preemptirqtest_##POSTFIX(int idx) \ + { \ + execute_preemptirqtest(idx); \ + } \ +/* + * We create 10 different functions, so that we can get 10 different + * backtraces. + */ +DECLARE_TESTFN(0) +DECLARE_TESTFN(1) +DECLARE_TESTFN(2) +DECLARE_TESTFN(3) +DECLARE_TESTFN(4) +DECLARE_TESTFN(5) +DECLARE_TESTFN(6) +DECLARE_TESTFN(7) +DECLARE_TESTFN(8) +DECLARE_TESTFN(9) + +static void (*testfuncs[])(int) = { + preemptirqtest_0, + preemptirqtest_1, + preemptirqtest_2, + preemptirqtest_3, + preemptirqtest_4, + preemptirqtest_5, + preemptirqtest_6, + preemptirqtest_7, + preemptirqtest_8, + preemptirqtest_9, +}; + +#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs) + +static int preemptirq_delay_run(void *data) +{ + int i; + int s = MIN(burst_size, NR_TEST_FUNCS); + + for (i = 0; i < s; i++) + (testfuncs[i])(i); return 0; } -static int __init preemptirq_delay_init(void) +static struct task_struct *preemptirq_start_test(void) { char task_name[50]; - struct task_struct *test_task; snprintf(task_name, sizeof(task_name), "%s_test", test_mode); + return kthread_run(preemptirq_delay_run, NULL, task_name); +} + + +static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t count) +{ + preemptirq_start_test(); + return count; +} + +static struct kobj_attribute trigger_attribute = + __ATTR(trigger, 0200, NULL, trigger_store); + +static struct attribute *attrs[] = { + &trigger_attribute.attr, + NULL, +}; + +static struct attribute_group attr_group = { + .attrs = attrs, +}; + +static struct kobject *preemptirq_delay_kobj; + +static int __init preemptirq_delay_init(void) +{ + struct task_struct *test_task; + int retval; + + test_task = preemptirq_start_test(); + retval = PTR_ERR_OR_ZERO(test_task); + if (retval != 0) + return retval; + + preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test", + kernel_kobj); + if (!preemptirq_delay_kobj) + return -ENOMEM; + + retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group); + if (retval) + kobject_put(preemptirq_delay_kobj); - test_task = kthread_run(preemptirq_delay_run, NULL, task_name); - return PTR_ERR_OR_ZERO(test_task); + return retval; } static void __exit preemptirq_delay_exit(void) { - return; + kobject_put(preemptirq_delay_kobj); } module_init(preemptirq_delay_init) -- 2.17.1