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Message-Id: <ee28d6e8b028a66a1d624895cf0aa04ddd17cb37.1623746916.git.bristot@redhat.com>
Date: Tue, 15 Jun 2021 11:28:51 +0200
From: Daniel Bristot de Oliveira <bristot@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Phil Auld <pauld@...hat.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Kate Carcia <kcarcia@...hat.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Jonathan Corbet <corbet@....net>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Clark Willaims <williams@...hat.com>,
John Kacur <jkacur@...hat.com>,
Juri Lelli <juri.lelli@...hat.com>,
Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH V4 12/12] trace/osnoise: Support hotplug operations
Enable and disable osnoise/timerlat thread during on CPU hotplug online
and offline operations respectivelly.
Cc: Jonathan Corbet <corbet@....net>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Alexandre Chartre <alexandre.chartre@...cle.com>
Cc: Clark Willaims <williams@...hat.com>
Cc: John Kacur <jkacur@...hat.com>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: linux-doc@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
---
kernel/trace/trace_osnoise.c | 133 +++++++++++++++++++++++++++--------
1 file changed, 103 insertions(+), 30 deletions(-)
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 2c1e2a074b1e..e8f057a3bdc3 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1399,22 +1399,67 @@ static int timerlat_main(void *data)
#endif /* CONFIG_TIMERLAT_TRACER */
/*
- * stop_per_cpu_kthread - stop per-cpu threads
+ * stop_kthread - stop a workload thread
+ */
+static void stop_kthread(unsigned int cpu)
+{
+ struct task_struct *kthread;
+
+ kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
+ if (kthread)
+ kthread_stop(kthread);
+ per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+}
+
+/*
+ * stop_per_cpu_kthread - Stop per-cpu threads
*
* Stop the osnoise sampling htread. Use this on unload and at system
* shutdown.
*/
static void stop_per_cpu_kthreads(void)
{
- struct task_struct *kthread;
int cpu;
- for_each_online_cpu(cpu) {
- kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
- if (kthread)
- kthread_stop(kthread);
- per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+ get_online_cpus();
+
+ for_each_online_cpu(cpu)
+ stop_kthread(cpu);
+
+ put_online_cpus();
+}
+
+/*
+ * start_kthread - Start a workload tread
+ */
+static int start_kthread(unsigned int cpu)
+{
+ struct task_struct *kthread;
+ char comm[24];
+ void *main = osnoise_main;
+
+#ifdef CONFIG_TIMERLAT_TRACER
+ if (osnoise_data.timerlat_tracer) {
+ snprintf(comm, 24, "timerlat/%d", cpu);
+ main = timerlat_main;
+ } else {
+ snprintf(comm, 24, "osnoise/%d", cpu);
+ }
+#else
+ snprintf(comm, 24, "osnoise/%d", cpu);
+#endif
+ kthread = kthread_create_on_cpu(main, NULL, cpu, comm);
+
+ if (IS_ERR(kthread)) {
+ pr_err(BANNER "could not start sampling thread\n");
+ stop_per_cpu_kthreads();
+ return -ENOMEM;
}
+
+ per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
+ wake_up_process(kthread);
+
+ return 0;
}
/*
@@ -1426,9 +1471,7 @@ static void stop_per_cpu_kthreads(void)
static int start_per_cpu_kthreads(struct trace_array *tr)
{
struct cpumask *current_mask = &save_cpumask;
- struct task_struct *kthread;
- char comm[24];
- void *main = osnoise_main;
+ int retval;
int cpu;
get_online_cpus();
@@ -1440,34 +1483,52 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
* And the CPU is online.
*/
cpumask_and(current_mask, cpu_online_mask, current_mask);
- put_online_cpus();
- for_each_online_cpu(cpu)
+ for_each_possible_cpu(cpu)
per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
for_each_cpu(cpu, current_mask) {
-#ifdef CONFIG_TIMERLAT_TRACER
- if (osnoise_data.timerlat_tracer) {
- snprintf(comm, 24, "timerlat/%d", cpu);
- main = timerlat_main;
- } else {
- snprintf(comm, 24, "osnoise/%d", cpu);
- }
-#else
- snprintf(comm, 24, "osnoise/%d", cpu);
-#endif
- kthread = kthread_create_on_cpu(main, NULL, cpu, comm);
-
- if (IS_ERR(kthread)) {
- pr_err(BANNER "could not start sampling thread\n");
+ retval = start_kthread(cpu);
+ if (retval) {
stop_per_cpu_kthreads();
- return -ENOMEM;
+ return retval;
}
-
- per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
- wake_up_process(kthread);
}
+ put_online_cpus();
+
+ return 0;
+}
+
+/*
+ * osnoise_cpu_init - CPU hotplug online callback function
+ */
+static int osnoise_cpu_init(unsigned int cpu)
+{
+ struct trace_array *tr = osnoise_trace;
+
+ if (!osnoise_busy)
+ return 0;
+
+ if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
+ return 0;
+
+ if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
+ return 0;
+
+ return start_kthread(cpu);
+}
+
+/*
+ * osnoise_cpu_die - CPU hotplug offline callback function
+ */
+static int osnoise_cpu_die(unsigned int cpu)
+{
+ if (!osnoise_busy)
+ return 0;
+
+ stop_kthread(cpu);
+
return 0;
}
@@ -1566,7 +1627,14 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
osnoise_tracer_stop(tr);
mutex_lock(&interface_lock);
+ /*
+ * osnoise_cpumask is ready by CPU hotplug operations.
+ */
+ get_online_cpus();
+
cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);
+
+ put_online_cpus();
mutex_unlock(&interface_lock);
if (running)
@@ -1924,6 +1992,11 @@ __init static int init_osnoise_tracer(void)
}
#endif
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/osnoise:online",
+ osnoise_cpu_init, osnoise_cpu_die);
+ if (ret < 0)
+ pr_warn(BANNER "Error to init cpu hotplug support\n");
+
init_tracefs();
return 0;
--
2.31.1
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