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Date:   Sun, 31 Oct 2021 19:04:56 +0100
From:   Daniel Bristot de Oliveira <>
To:     Steven Rostedt <>
Cc:     Daniel Bristot de Oliveira <>,
        Ingo Molnar <>,
        Tom Zanussi <>,
        Masami Hiramatsu <>,
        Juri Lelli <>,
        Clark Williams <>,
        John Kacur <>,
        Peter Zijlstra <>,
        Thomas Gleixner <>,
        Sebastian Andrzej Siewior <>,,,
Subject: [PATCH V9 1/9] tracing/osnoise: Do not follow tracing_cpumask

In preparation to support multiple instances, decouple the
osnoise/timelat workload from instance-specific tracing_cpumask.

Different instances can have conflicting cpumasks, making osnoise
workload management needlessly complex. Osnoise already has its
global cpumask.

I also thought about using the first instance mask, but the
"first" instance could be removed before the others.

This also fixes the problem that changing the tracing_mask was not
re-starting the trace.

Cc: Steven Rostedt <>
Cc: Ingo Molnar <>
Cc: Tom Zanussi <>
Cc: Masami Hiramatsu <>
Cc: Juri Lelli <>
Cc: Clark Williams <>
Cc: John Kacur <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Cc: Sebastian Andrzej Siewior <>
Cc: Daniel Bristot de Oliveira <>
Signed-off-by: Daniel Bristot de Oliveira <>
 kernel/trace/trace_osnoise.c | 24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index d11b41784fac..ceff407655a5 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1554,13 +1554,9 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
-	 * Run only on CPUs in which trace and osnoise are allowed to run.
+	 * Run only on online CPUs in which osnoise is allowed to run.
-	cpumask_and(current_mask, tr->tracing_cpumask, &osnoise_cpumask);
-	/*
-	 * And the CPU is online.
-	 */
-	cpumask_and(current_mask, cpu_online_mask, current_mask);
+	cpumask_and(current_mask, cpu_online_mask, &osnoise_cpumask);
 		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
@@ -1581,10 +1577,8 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 static void osnoise_hotplug_workfn(struct work_struct *dummy)
-	struct trace_array *tr = osnoise_trace;
 	unsigned int cpu = smp_processor_id();
 	if (!osnoise_busy)
@@ -1596,9 +1590,6 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy)
 	if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
 		goto out_unlock;
-	if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
-		goto out_unlock;
@@ -1701,13 +1692,10 @@ static void osnoise_tracer_stop(struct trace_array *tr);
  * interface to the osnoise trace. By default, it lists all  CPUs,
  * in this way, allowing osnoise threads to run on any online CPU
  * of the system. It serves to restrict the execution of osnoise to the
- * set of CPUs writing via this interface. Note that osnoise also
- * respects the "tracing_cpumask." Hence, osnoise threads will run only
- * on the set of CPUs allowed here AND on "tracing_cpumask." Why not
- * have just "tracing_cpumask?" Because the user might be interested
- * in tracing what is running on other CPUs. For instance, one might
- * run osnoise in one HT CPU while observing what is running on the
- * sibling HT CPU.
+ * set of CPUs writing via this interface. Why not use "tracing_cpumask"?
+ * Because the user might be interested in tracing what is running on
+ * other CPUs. For instance, one might run osnoise in one HT CPU
+ * while observing what is running on the sibling HT CPU.
 static ssize_t
 osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,

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