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.

Link: https://lkml.kernel.org/r/169a71bcc919ce3ab53ae6f9ca5cde57fffaf9c6.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index d11b41784fac8fa52a4bf6c483614a73bb782103..ceff407655a52c6e7145cd616c61efd57ad37fb4 100644 (file)
--- 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)
 
        cpus_read_lock();
        /*
-        * 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);
 
        for_each_possible_cpu(cpu)
                per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
@@ -1581,10 +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)
@@ -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;
-
        start_kthread(cpu);
 
 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,