linux-kernel - [PATCH 5/5] tracing: Have function_graph selftest call cond

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Message-Id: <20230528051742.1325503-6-rostedt@goodmis.org>
Date:   Sun, 28 May 2023 01:17:42 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        Linux trace kernel <linux-trace-kernel@...r.kernel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: [PATCH 5/5] tracing: Have function_graph selftest call cond_resched()

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

When all kernel debugging is enabled (lockdep, KSAN, etc), the function
graph enabling and disabling can take several seconds to complete. The
function_graph selftest enables and disables function graph tracing
several times. With full debugging enabled, the soft lockup watchdog was
triggering because the selftest was running without ever scheduling.

Add cond_resched() throughout the test to make sure it does not trigger
the soft lockup detector.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_selftest.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index a931d9aaea26..529590499b1f 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -848,6 +848,12 @@ trace_selftest_startup_function_graph(struct tracer *trace,
 	}
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	/*
+	 * These tests can take some time to run. Make sure on non PREEMPT
+	 * kernels, we do not trigger the softlockup detector.
+	 */
+	cond_resched();
+
 	tracing_reset_online_cpus(&tr->array_buffer);
 	set_graph_array(tr);
 
@@ -869,6 +875,8 @@ trace_selftest_startup_function_graph(struct tracer *trace,
 	if (ret)
 		goto out;
 
+	cond_resched();
+
 	ret = register_ftrace_graph(&fgraph_ops);
 	if (ret) {
 		warn_failed_init_tracer(trace, ret);
@@ -891,6 +899,8 @@ trace_selftest_startup_function_graph(struct tracer *trace,
 	if (ret)
 		goto out;
 
+	cond_resched();
+
 	tracing_start();
 
 	if (!ret && !count) {
-- 
2.39.2