linux-kernel - [PATCH rcu 01/11] torture: Add get_torture_init

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Message-Id: <20250219153938.24966-2-boqun.feng@gmail.com>
Date: Wed, 19 Feb 2025 07:39:28 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>,	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Huth <thuth@...hat.com>,	"Borislav Petkov (AMD)" <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,	Yury Norov <yury.norov@...il.com>,
	Valentin Schneider <vschneid@...hat.com>,	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,	linux-trace-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH rcu 01/11] torture: Add get_torture_init_jiffies() for test-start time

From: "Paul E. McKenney" <paulmck@...nel.org>

This commit adds a get_torture_init_jiffies() function that returns the
value of the jiffies counter at the start of the test, that is, at the
point where torture_init_begin() was invoked.

This will be used to enable torture-test holdoffs for tests implemented
using per-CPU kthreads, which are created and deleted by CPU-hotplug
operations, and thus (unlike normal kthreads) don't automatically know
when the test started.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 include/linux/torture.h |  1 +
 kernel/torture.c        | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 0134e7221cae..1b59056c3b18 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -104,6 +104,7 @@ int torture_stutter_init(int s, int sgap);
 /* Initialization and cleanup. */
 bool torture_init_begin(char *ttype, int v);
 void torture_init_end(void);
+unsigned long get_torture_init_jiffies(void);
 bool torture_cleanup_begin(void);
 void torture_cleanup_end(void);
 bool torture_must_stop(void);
diff --git a/kernel/torture.c b/kernel/torture.c
index dede150aef01..3a0a8cc60401 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -792,6 +792,8 @@ static void torture_stutter_cleanup(void)
 	stutter_task = NULL;
 }
 
+static unsigned long torture_init_jiffies;
+
 static void
 torture_print_module_parms(void)
 {
@@ -821,6 +823,7 @@ bool torture_init_begin(char *ttype, int v)
 	torture_type = ttype;
 	verbose = v;
 	fullstop = FULLSTOP_DONTSTOP;
+	WRITE_ONCE(torture_init_jiffies, jiffies); // Lockless reads.
 	torture_print_module_parms();
 	return true;
 }
@@ -836,6 +839,15 @@ void torture_init_end(void)
 }
 EXPORT_SYMBOL_GPL(torture_init_end);
 
+/*
+ * Get the torture_init_begin()-time value of the jiffies counter.
+ */
+unsigned long get_torture_init_jiffies(void)
+{
+	return READ_ONCE(torture_init_jiffies);
+}
+EXPORT_SYMBOL_GPL(get_torture_init_jiffies);
+
 /*
  * Clean up torture module.  Please note that this is -not- invoked via
  * the usual module_exit() mechanism, but rather by an explicit call from
-- 
2.39.5 (Apple Git-154)