linux-kernel - [PATCH 1/5] trace/osnoise: Do not follow tracing

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Message-Id: <db14a8eef9af9b9de665251b729361bee75a70a4.1628775552.git.bristot@kernel.org>
Date:   Thu, 12 Aug 2021 15:57:20 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-trace-devel@...r.kernel.org
Subject: [PATCH 1/5] trace/osnoise: Do not follow tracing_cpumask

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

Different instances can have conflicing cpumasks, making osnoise
workload management needlessly complex. Osnoise already have its
global cpu mask.

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 <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Tom Zanussi <zanussi@...nel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Daniel Bristot de Oliveira <bristot@...nel.org>
Cc: linux-trace-devel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Daniel Bristot de Oliveira (Red Hat) <bristot@...nel.org>
---
 kernel/trace/trace_osnoise.c | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index b576e96d9741..aadb0d110155 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1553,13 +1553,10 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 
 	get_online_cpus();
 	/*
-	 * Run only on CPUs in which trace and osnoise are allowed to run.
+	 * Run only on online CPUs in which trace and osnoise are 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);
 
 	for_each_possible_cpu(cpu)
 		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
@@ -1580,10 +1577,8 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 #ifdef CONFIG_HOTPLUG_CPU
 static void osnoise_hotplug_workfn(struct work_struct *dummy)
 {
-	struct trace_array *tr = osnoise_trace;
 	unsigned int cpu = smp_processor_id();
 
-
 	mutex_lock(&trace_types_lock);
 
 	if (!osnoise_busy)
@@ -1595,9 +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;
-
 	start_kthread(cpu);
 
 out_unlock:
@@ -1700,13 +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,
-- 
2.31.1