1 files changed, 236 insertions, 8 deletions

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 4300c5dc4e5d..94c1b5eb1dc0 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -49,6 +49,28 @@
 #define DEFAULT_TIMERLAT_PRIO	95			/* FIFO 95 */
 
 /*
+ * osnoise/options entries.
+ */
+enum osnoise_options_index {
+	OSN_DEFAULTS = 0,
+	OSN_WORKLOAD,
+	OSN_PANIC_ON_STOP,
+	OSN_PREEMPT_DISABLE,
+	OSN_IRQ_DISABLE,
+	OSN_MAX
+};
+
+static const char * const osnoise_options_str[OSN_MAX] = {
+							"DEFAULTS",
+							"OSNOISE_WORKLOAD",
+							"PANIC_ON_STOP",
+							"OSNOISE_PREEMPT_DISABLE",
+							"OSNOISE_IRQ_DISABLE" };
+
+#define OSN_DEFAULT_OPTIONS		0x2
+static unsigned long osnoise_options	= OSN_DEFAULT_OPTIONS;
+
+/*
  * trace_array of the enabled osnoise/timerlat instances.
  */
 struct osnoise_instance {
@@ -1173,11 +1195,12 @@ trace_sched_switch_callback(void *data, bool preempt,
 			    unsigned int prev_state)
 {
 	struct osnoise_variables *osn_var = this_cpu_osn_var();
+	int workload = test_bit(OSN_WORKLOAD, &osnoise_options);
 
-	if (p->pid != osn_var->pid)
+	if ((p->pid != osn_var->pid) || !workload)
 		thread_exit(osn_var, p);
 
-	if (n->pid != osn_var->pid)
+	if ((n->pid != osn_var->pid) || !workload)
 		thread_entry(osn_var, n);
 }
 
@@ -1255,6 +1278,9 @@ static __always_inline void osnoise_stop_tracing(void)
 		trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
 				"stop tracing hit on cpu %d\n", smp_processor_id());
 
+		if (test_bit(OSN_PANIC_ON_STOP, &osnoise_options))
+			panic("tracer hit stop condition on CPU %d\n", smp_processor_id());
+
 		tracer_tracing_off(tr);
 	}
 	rcu_read_unlock();
@@ -1289,12 +1315,14 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool disable_irq = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
 	struct osnoise_variables *osn_var = this_cpu_osn_var();
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;
 	s64 noise = 0, max_noise = 0;
 	s64 total, last_total = 0;
 	struct osnoise_sample s;
+	bool disable_preemption;
 	unsigned int threshold;
 	u64 runtime, stop_in;
 	u64 sum_noise = 0;
@@ -1302,6 +1330,12 @@ static int run_osnoise(void)
 	int ret = -1;
 
 	/*
+	 * Disabling preemption is only required if IRQs are enabled,
+	 * and the options is set on.
+	 */
+	disable_preemption = !disable_irq && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+
+	/*
 	 * Considers the current thread as the workload.
 	 */
 	osn_var->pid = current->pid;
@@ -1317,6 +1351,15 @@ static int run_osnoise(void)
 	threshold = tracing_thresh ? : 5000;
 
 	/*
+	 * Apply PREEMPT and IRQ disabled options.
+	 */
+	if (disable_irq)
+		local_irq_disable();
+
+	if (disable_preemption)
+		preempt_disable();
+
+	/*
 	 * Make sure NMIs see sampling first
 	 */
 	osn_var->sampling = true;
@@ -1403,16 +1446,21 @@ static int run_osnoise(void)
 		 * cond_resched()
 		 */
 		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
-			local_irq_disable();
+			if (!disable_irq)
+				local_irq_disable();
+
 			rcu_momentary_dyntick_idle();
-			local_irq_enable();
+
+			if (!disable_irq)
+				local_irq_enable();
 		}
 
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
-		 * they so wish.
+		 * they so wish, unless set not do to so.
 		 */
-		cond_resched();
+		if (!disable_irq && !disable_preemption)
+			cond_resched();
 
 		last_sample = sample;
 		last_int_count = int_count;
@@ -1432,6 +1480,15 @@ static int run_osnoise(void)
 	barrier();
 
 	/*
+	 * Return to the preemptive state.
+	 */
+	if (disable_preemption)
+		preempt_enable();
+
+	if (disable_irq)
+		local_irq_enable();
+
+	/*
 	 * Save noise info.
 	 */
 	s.noise = time_to_us(sum_noise);
@@ -1710,9 +1767,16 @@ static void stop_kthread(unsigned int cpu)
 	struct task_struct *kthread;
 
 	kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
-	if (kthread)
+	if (kthread) {
 		kthread_stop(kthread);
-	per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+	} else {
+		if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+			per_cpu(per_cpu_osnoise_var, cpu).sampling = false;
+			barrier();
+			return;
+		}
+	}
 }
 
 /*
@@ -1746,6 +1810,13 @@ static int start_kthread(unsigned int cpu)
 		snprintf(comm, 24, "timerlat/%d", cpu);
 		main = timerlat_main;
 	} else {
+		/* if no workload, just return */
+		if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+			per_cpu(per_cpu_osnoise_var, cpu).sampling = true;
+			barrier();
+			return 0;
+		}
+
 		snprintf(comm, 24, "osnoise/%d", cpu);
 	}
 
@@ -1861,6 +1932,150 @@ static void osnoise_init_hotplug_support(void)
 #endif /* CONFIG_HOTPLUG_CPU */
 
 /*
+ * seq file functions for the osnoise/options file.
+ */
+static void *s_options_start(struct seq_file *s, loff_t *pos)
+{
+	int option = *pos;
+
+	mutex_lock(&interface_lock);
+
+	if (option >= OSN_MAX)
+		return NULL;
+
+	return pos;
+}
+
+static void *s_options_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	int option = ++(*pos);
+
+	if (option >= OSN_MAX)
+		return NULL;
+
+	return pos;
+}
+
+static int s_options_show(struct seq_file *s, void *v)
+{
+	loff_t *pos = v;
+	int option = *pos;
+
+	if (option == OSN_DEFAULTS) {
+		if (osnoise_options == OSN_DEFAULT_OPTIONS)
+			seq_printf(s, "%s", osnoise_options_str[option]);
+		else
+			seq_printf(s, "NO_%s", osnoise_options_str[option]);
+		goto out;
+	}
+
+	if (test_bit(option, &osnoise_options))
+		seq_printf(s, "%s", osnoise_options_str[option]);
+	else
+		seq_printf(s, "NO_%s", osnoise_options_str[option]);
+
+out:
+	if (option != OSN_MAX)
+		seq_puts(s, " ");
+
+	return 0;
+}
+
+static void s_options_stop(struct seq_file *s, void *v)
+{
+	seq_puts(s, "\n");
+	mutex_unlock(&interface_lock);
+}
+
+static const struct seq_operations osnoise_options_seq_ops = {
+	.start		= s_options_start,
+	.next		= s_options_next,
+	.show		= s_options_show,
+	.stop		= s_options_stop
+};
+
+static int osnoise_options_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &osnoise_options_seq_ops);
+};
+
+/**
+ * osnoise_options_write - Write function for "options" entry
+ * @filp: The active open file structure
+ * @ubuf: The user buffer that contains the value to write
+ * @cnt: The maximum number of bytes to write to "file"
+ * @ppos: The current position in @file
+ *
+ * Writing the option name sets the option, writing the "NO_"
+ * prefix in front of the option name disables it.
+ *
+ * Writing "DEFAULTS" resets the option values to the default ones.
+ */
+static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf,
+				     size_t cnt, loff_t *ppos)
+{
+	int running, option, enable, retval;
+	char buf[256], *option_str;
+
+	if (cnt >= 256)
+		return -EINVAL;
+
+	if (copy_from_user(buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	if (strncmp(buf, "NO_", 3)) {
+		option_str = strstrip(buf);
+		enable = true;
+	} else {
+		option_str = strstrip(&buf[3]);
+		enable = false;
+	}
+
+	option = match_string(osnoise_options_str, OSN_MAX, option_str);
+	if (option < 0)
+		return -EINVAL;
+
+	/*
+	 * trace_types_lock is taken to avoid concurrency on start/stop.
+	 */
+	mutex_lock(&trace_types_lock);
+	running = osnoise_has_registered_instances();
+	if (running)
+		stop_per_cpu_kthreads();
+
+	mutex_lock(&interface_lock);
+	/*
+	 * avoid CPU hotplug operations that might read options.
+	 */
+	cpus_read_lock();
+
+	retval = cnt;
+
+	if (enable) {
+		if (option == OSN_DEFAULTS)
+			osnoise_options = OSN_DEFAULT_OPTIONS;
+		else
+			set_bit(option, &osnoise_options);
+	} else {
+		if (option == OSN_DEFAULTS)
+			retval = -EINVAL;
+		else
+			clear_bit(option, &osnoise_options);
+	}
+
+	cpus_read_unlock();
+	mutex_unlock(&interface_lock);
+
+	if (running)
+		start_per_cpu_kthreads();
+	mutex_unlock(&trace_types_lock);
+
+	return retval;
+}
+
+/*
  * osnoise_cpus_read - Read function for reading the "cpus" file
  * @filp: The active open file structure
  * @ubuf: The userspace provided buffer to read value into
@@ -2042,6 +2257,14 @@ static const struct file_operations cpus_fops = {
 	.llseek		= generic_file_llseek,
 };
 
+static const struct file_operations osnoise_options_fops = {
+	.open		= osnoise_options_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+	.write		= osnoise_options_write
+};
+
 #ifdef CONFIG_TIMERLAT_TRACER
 #ifdef CONFIG_STACKTRACE
 static int init_timerlat_stack_tracefs(struct dentry *top_dir)
@@ -2128,6 +2351,11 @@ static int init_tracefs(void)
 	if (!tmp)
 		goto err;
 
+	tmp = trace_create_file("options", TRACE_MODE_WRITE, top_dir, NULL,
+				&osnoise_options_fops);
+	if (!tmp)
+		goto err;
+
 	ret = init_timerlat_tracefs(top_dir);
 	if (ret)
 		goto err;