[for-next][PATCH 0/2] tracing: Latency updates for 7.2

[for-next][PATCH 0/2] tracing: Latency updates for 7.2

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
latency/for-next

Head SHA1: 9cb99c598643ba78638dfd668cf020544159cf70


Crystal Wood (2):
      tracing/osnoise: Dump stack on timerlat uret threshold event
      tracing/osnoise: Array printk init and cleanup

----
 kernel/trace/trace_osnoise.c | 46 ++++++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

[for-next][PATCH 1/2] tracing/osnoise: Dump stack on timerlat uret threshold event

[Steven Rostedt]

From: Crystal Wood <crwood@redhat.com>

Dump the saved IRQ stack trace regardless of whether the event was
THREAD_CONTEXT or THREAD_URET.

In the uret case, the latency presumably had not yet crossed the
threshold at IRQ time (or else it would have dumped the stack at thread
wakeup time, unless we're racing with a change to the threshold), but it
may have at least contributed -- and this is possible with THREAD_CONTEXT
as well.

In any case, it helps with writing reliable rtla tests if we always get
a stack trace on a threshold event.

Cc: John Kacur <jkacur@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Costa Shulyupin <costa.shul@redhat.com>
Cc: Wander Lairson Costa <wander@redhat.com>
Link: https://patch.msgid.link/20260511223143.1477332-1-crwood@redhat.com
Signed-off-by: Crystal Wood <crwood@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_osnoise.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 75678053b21c..62c2667d97fa 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2544,9 +2544,12 @@ timerlat_fd_read(struct file *file, char __user *ubuf, size_t count,
 		notify_new_max_latency(diff);
 
 		tlat->tracing_thread = false;
-		if (osnoise_data.stop_tracing_total)
-			if (time_to_us(diff) >= osnoise_data.stop_tracing_total)
+		if (osnoise_data.stop_tracing_total) {
+			if (time_to_us(diff) >= osnoise_data.stop_tracing_total) {
+				timerlat_dump_stack(time_to_us(diff));
 				osnoise_stop_tracing();
+			}
+		}
 	} else {
 		tlat->tracing_thread = false;
 		tlat->kthread = current;
-- 
2.53.0

[for-next][PATCH 2/2] tracing/osnoise: Array printk init and cleanup

[Steven Rostedt]

From: Crystal Wood <crwood@redhat.com>

None of the calls to trace_array_printk_buf() will do anything
if we don't initialize the buffer on instance creation (unless
some other tracer called it), so do that.

Add an osnoise_print() function to facilitate adding debug prints
(without tainting).

Use trace_array_printk() instead of trace_array_printk_buf(), as we're
only writing to the main buffer (of a non-main instance) anyway -- and
trace_array_printk_buf() skips the check to make sure we're not printing
to the global instance.

Link: https://patch.msgid.link/20260511223035.1475676-1-crwood@redhat.com
Signed-off-by: Crystal Wood <crwood@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_osnoise.c | 39 ++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 62c2667d97fa..5e83c4f6f2b4 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -83,6 +83,22 @@ struct osnoise_instance {
 
 static struct list_head osnoise_instances;
 
+static void osnoise_print(const char *fmt, ...)
+{
+	struct osnoise_instance *inst;
+	struct trace_array *tr;
+	va_list ap;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
+		tr = inst->tr;
+		va_start(ap, fmt);
+		trace_array_vprintk(tr, _RET_IP_, fmt, ap);
+		va_end(ap);
+	}
+	rcu_read_unlock();
+}
+
 static bool osnoise_has_registered_instances(void)
 {
 	return !!list_first_or_null_rcu(&osnoise_instances,
@@ -123,6 +139,7 @@ static int osnoise_register_instance(struct trace_array *tr)
 	 * trace_types_lock.
 	 */
 	lockdep_assert_held(&trace_types_lock);
+	trace_array_init_printk(tr);
 
 	inst = kmalloc_obj(*inst);
 	if (!inst)
@@ -471,15 +488,7 @@ static void print_osnoise_headers(struct seq_file *s)
  * osnoise_taint - report an osnoise error.
  */
 #define osnoise_taint(msg) ({							\
-	struct osnoise_instance *inst;						\
-	struct trace_buffer *buffer;						\
-										\
-	rcu_read_lock();							\
-	list_for_each_entry_rcu(inst, &osnoise_instances, list) {		\
-		buffer = inst->tr->array_buffer.buffer;				\
-		trace_array_printk_buf(buffer, _THIS_IP_, msg);			\
-	}									\
-	rcu_read_unlock();							\
+	osnoise_print(msg);							\
 	osnoise_data.tainted = true;						\
 })
 
@@ -1189,10 +1198,10 @@ static __always_inline void osnoise_stop_exception(char *msg, int cpu)
 	rcu_read_lock();
 	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
 		tr = inst->tr;
-		trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
-				       "stop tracing hit on cpu %d due to exception: %s\n",
-				       smp_processor_id(),
-				       msg);
+		trace_array_printk(tr, _THIS_IP_,
+				   "stop tracing hit on cpu %d due to exception: %s\n",
+				   smp_processor_id(),
+				   msg);
 
 		if (test_bit(OSN_PANIC_ON_STOP, &osnoise_options))
 			panic("tracer hit on cpu %d due to exception: %s\n",
@@ -1362,8 +1371,8 @@ static __always_inline void osnoise_stop_tracing(void)
 	rcu_read_lock();
 	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
 		tr = inst->tr;
-		trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
-				"stop tracing hit on cpu %d\n", smp_processor_id());
+		trace_array_printk(tr, _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());
-- 
2.53.0