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tracing latency updates for 7.2:

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- Dump the stack to the buffer on timerlat uret threashold event
 
   Record the stack trace in the buffer for THREAD_URET as well as
   THREAD_CONTEXT when the threshold is hit. Otherwise, if the threshold was
   not hit at task wakeup, but was at task return, it will not produce a
   stack trace making it harder to debug.
 
 - Have osnoise trace prints print to all buffers
 
   The osnoise tracer is allowed to print to the main buffer. Add a
   osnoise_print() helper function and use trace_array_vprintk() to print
   osnoise output.
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Merge tag 'trace-latency-v7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing latency updates from Steven Rostedt:

 - Dump the stack to the buffer on timerlat uret threashold event

   Record the stack trace in the buffer for THREAD_URET as well as
   THREAD_CONTEXT when the threshold is hit. Otherwise, if the threshold
   was not hit at task wakeup, but was at task return, it will not
   produce a stack trace making it harder to debug.

 - Have osnoise trace prints print to all buffers

   The osnoise tracer is allowed to print to the main buffer. Add a
   osnoise_print() helper function and use trace_array_vprintk() to
   print osnoise output.

* tag 'trace-latency-v7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/osnoise: Array printk init and cleanup
  tracing/osnoise: Dump stack on timerlat uret threshold event
This commit is contained in:
Linus Torvalds 2026-06-16 17:38:19 +05:30
commit c071a4fbb0
1 changed files with 29 additions and 17 deletions
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46
kernel/trace/trace_osnoise.c
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@ -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());
@ -2544,9 +2553,12 @@ 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;