From patchwork Fri Oct 21 01:00:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13014171 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 BB1A3C433FE for ; Fri, 21 Oct 2022 01:00:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229933AbiJUBA4 (ORCPT ); Thu, 20 Oct 2022 21:00:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229832AbiJUBAz (ORCPT ); Thu, 20 Oct 2022 21:00:55 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F39CA1A16EA; Thu, 20 Oct 2022 18:00:53 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6DA1461D79; Fri, 21 Oct 2022 01:00:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CA1C6C433D7; Fri, 21 Oct 2022 01:00:51 +0000 (UTC) Date: Thu, 20 Oct 2022 21:00:56 -0400 From: Steven Rostedt To: LKML Cc: Linux Trace Kernel , Masami Hiramatsu , Andrew Morton , Mathieu Desnoyers , , Joel Fernandes , Tom Zanussi , Ross Zwisler Subject: [PATCH v2] tracing: Add trace_trigger kernel command line option Message-ID: <20221020210056.0d8d0a5b@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: "Steven Rostedt (Google)" Allow triggers to be enabled at kernel boot up. For example: trace_trigger="sched_switch.stacktrace if prev_state == 2" The above will enable the stacktrace trigger on top of the sched_switch event and only trigger if its prev_state is 2 (TASK_UNINTERRUPTIBLE). Then at boot up, a stacktrace will trigger and be recorded in the tracing ring buffer every time the sched_switch happens where the previous state is TASK_INTERRUPTIBLE. Another useful trigger would be "traceoff" which can stop tracing on an event if a field of the event matches a certain value defined by the filter ("if" statement). Signed-off-by: Steven Rostedt (Google) --- Changes since v1: https://lore.kernel.org/all/20221019200137.70343645@gandalf.local.home/ - Encapsulated trigger code better to get rid of warning of unused 'i' variable (kernel-test-robot) - Removed synchronize_rcu() avoidance, as Paul McKenney will be updating it to not cause issues: https://lore.kernel.org/all/20221020222108.GZ5600@paulmck-ThinkPad-P17-Gen-1/ .../admin-guide/kernel-parameters.txt | 19 +++++ kernel/trace/trace_events.c | 72 ++++++++++++++++++- 2 files changed, 89 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a465d5242774..ccf91a4bf113 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6257,6 +6257,25 @@ See also Documentation/trace/ftrace.rst "trace options" section. + trace_trigger=[trigger-list] + [FTRACE] Add a event trigger on specific events. + Set a trigger on top of a specific event, with an optional + filter. + + The format is is "trace_trigger=.[ if ],..." + Where more than one trigger may be specified that are comma deliminated. + + For example: + + trace_trigger="sched_switch.stacktrace if prev_state == 2" + + The above will enable the "stacktrace" trigger on the "sched_switch" + event but only trigger it if the "prev_state" of the "sched_switch" + event is "2" (TASK_UNINTERUPTIBLE). + + See also "Event triggers" in Documentation/trace/events.rst + + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 0356cae0cf74..7372fffb8109 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2796,6 +2796,44 @@ trace_create_new_event(struct trace_event_call *call, return file; } +#ifdef CONFIG_HIST_TRIGGERS +#define MAX_BOOT_TRIGGERS 32 + +static struct boot_triggers { + const char *event; + char *trigger; +} bootup_triggers[MAX_BOOT_TRIGGERS]; + +static char bootup_trigger_buf[COMMAND_LINE_SIZE]; +static int nr_boot_triggers; + +static __init int setup_trace_triggers(char *str) +{ + char *trigger; + char *buf; + int i; + + strlcpy(bootup_trigger_buf, str, COMMAND_LINE_SIZE); + ring_buffer_expanded = true; + disable_tracing_selftest("running event triggers"); + + buf = bootup_trigger_buf; + for (i = 0; i < MAX_BOOT_TRIGGERS; i++) { + trigger = strsep(&buf, ","); + if (!trigger) + break; + bootup_triggers[i].event = strsep(&trigger, "."); + bootup_triggers[i].trigger = strsep(&trigger, "."); + if (!bootup_triggers[i].trigger) + break; + } + + nr_boot_triggers = i; + return 1; +} +__setup("trace_trigger=", setup_trace_triggers); +#endif + /* Add an event to a trace directory */ static int __trace_add_new_event(struct trace_event_call *call, struct trace_array *tr) @@ -2812,6 +2850,28 @@ __trace_add_new_event(struct trace_event_call *call, struct trace_array *tr) return event_define_fields(call); } +#ifdef CONFIG_HIST_TRIGGERS +static void trace_early_triggers(struct trace_event_file *file, const char *name) +{ + int ret; + int i; + + for (i = 0; i < nr_boot_triggers; i++) { + if (strcmp(name, bootup_triggers[i].event)) + continue; + mutex_lock(&event_mutex); + ret = trigger_process_regex(file, bootup_triggers[i].trigger); + mutex_unlock(&event_mutex); + if (ret) + pr_err("Failed to register trigger '%s' on event %s\n", + bootup_triggers[i].trigger, + bootup_triggers[i].event); + } +} +#else +static inline void trace_early_triggers(struct trace_event_file *file, const char *name) { } +#endif + /* * Just create a descriptor for early init. A descriptor is required * for enabling events at boot. We want to enable events before @@ -2822,12 +2882,19 @@ __trace_early_add_new_event(struct trace_event_call *call, struct trace_array *tr) { struct trace_event_file *file; + int ret; file = trace_create_new_event(call, tr); if (!file) return -ENOMEM; - return event_define_fields(call); + ret = event_define_fields(call); + if (ret) + return ret; + + trace_early_triggers(file, trace_event_name(call)); + + return 0; } struct ftrace_module_file_ops; @@ -3726,6 +3793,8 @@ static __init int event_trace_enable(void) list_add(&call->list, &ftrace_events); } + register_trigger_cmds(); + /* * We need the top trace array to have a working set of trace * points at early init, before the debug files and directories @@ -3740,7 +3809,6 @@ static __init int event_trace_enable(void) register_event_cmds(); - register_trigger_cmds(); return 0; }