Patch "tracing/osnoise: Make osnoise_main to sleep for microseconds" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tracing/osnoise: Make osnoise_main to sleep for microseconds

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tracing-osnoise-make-osnoise_main-to-sleep-for-micro.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 437a8752a71a3d3fb40396b721acbfafa0f76139
Author: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Date:   Fri Feb 18 16:17:38 2022 +0100

    tracing/osnoise: Make osnoise_main to sleep for microseconds
    
    [ Upstream commit dd990352f01ee9a6c6eee152e5d11c021caccfe4 ]
    
    osnoise's runtime and period are in the microseconds scale, but it is
    currently sleeping in the millisecond's scale. This behavior roots in the
    usage of hwlat as the skeleton for osnoise.
    
    Make osnoise to sleep in the microseconds scale. Also, move the sleep to
    a specialized function.
    
    Link: https://lkml.kernel.org/r/302aa6c7bdf2d131719b22901905e9da122a11b2.1645197336.git.bristot@xxxxxxxxxx
    
    Cc: Ingo Molnar <mingo@xxxxxxxxxx>
    Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
    Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 65a518649997..fc491d0aee5a 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1249,6 +1249,37 @@ static int run_osnoise(void)
 static struct cpumask osnoise_cpumask;
 static struct cpumask save_cpumask;
 
+/*
+ * osnoise_sleep - sleep until the next period
+ */
+static void osnoise_sleep(void)
+{
+	u64 interval;
+	ktime_t wake_time;
+
+	mutex_lock(&interface_lock);
+	interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
+	mutex_unlock(&interface_lock);
+
+	/*
+	 * differently from hwlat_detector, the osnoise tracer can run
+	 * without a pause because preemption is on.
+	 */
+	if (!interval) {
+		/* Let synchronize_rcu_tasks() make progress */
+		cond_resched_tasks_rcu_qs();
+		return;
+	}
+
+	wake_time = ktime_add_us(ktime_get(), interval);
+	__set_current_state(TASK_INTERRUPTIBLE);
+
+	while (schedule_hrtimeout_range(&wake_time, 0, HRTIMER_MODE_ABS)) {
+		if (kthread_should_stop())
+			break;
+	}
+}
+
 /*
  * osnoise_main - The osnoise detection kernel thread
  *
@@ -1257,30 +1288,10 @@ static struct cpumask save_cpumask;
  */
 static int osnoise_main(void *data)
 {
-	u64 interval;
 
 	while (!kthread_should_stop()) {
-
 		run_osnoise();
-
-		mutex_lock(&interface_lock);
-		interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
-		mutex_unlock(&interface_lock);
-
-		do_div(interval, USEC_PER_MSEC);
-
-		/*
-		 * differently from hwlat_detector, the osnoise tracer can run
-		 * without a pause because preemption is on.
-		 */
-		if (interval < 1) {
-			/* Let synchronize_rcu_tasks() make progress */
-			cond_resched_tasks_rcu_qs();
-			continue;
-		}
-
-		if (msleep_interruptible(interval))
-			break;
+		osnoise_sleep();
 	}
 
 	return 0;