include/trace/events/irq.h | 47 ++++++++++++++++++++++++++++++++++++++ kernel/softirq.c | 9 ++++++-- 2 files changed, 54 insertions(+), 2 deletions(-)
commit f4bf3ca2e5cba655824b6e0893a98dfb33ed24e5 upstream.
Tasklets are supposed to finish their work quickly and should not block the
current running process, but it is not guaranteed that they do so.
Currently softirq_entry/exit can be used to analyse the total tasklets
execution time, but that's not helpful to track individual tasklets
execution time. That makes it hard to identify tasklet functions, which
take more time than expected.
Add tasklet_entry/exit trace point support to track individual tasklet
execution.
Trivial usage example:
# echo 1 > /sys/kernel/debug/tracing/events/irq/tasklet_entry/enable
# echo 1 > /sys/kernel/debug/tracing/events/irq/tasklet_exit/enable
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 4/4 #P:4
#
# _-----=> irqs-off/BH-disabled
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
<idle>-0 [003] ..s1. 314.011428: tasklet_entry: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
<idle>-0 [003] ..s1. 314.011432: tasklet_exit: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
<idle>-0 [003] ..s1. 314.017369: tasklet_entry: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
<idle>-0 [003] ..s1. 314.017371: tasklet_exit: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
Signed-off-by: J. Avila <elavila@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230407230526.1685443-1-jstultz@google.com
[elavila: Port to android-mainline]
[jstultz: Rebased to upstream, cut unused trace points, added
comments for the tracepoints, reworded commit]
The intention is to keep the stable branch in sync with upstream fixes
and improve observability without introducing new functionality.
Signed-off-by: Sumanth Gavini <sumanth.gavini@yahoo.com>
Changes in V2:
- No code changes
- Link to V1: https://lore.kernel.org/all/20250812161755.609600-1-sumanth.gavini@yahoo.com/
- Updated the comment msg before the signed-off-by
---
include/trace/events/irq.h | 47 ++++++++++++++++++++++++++++++++++++++
kernel/softirq.c | 9 ++++++--
2 files changed, 54 insertions(+), 2 deletions(-)
diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index eeceafaaea4c..a07b4607b663 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -160,6 +160,53 @@ DEFINE_EVENT(softirq, softirq_raise,
TP_ARGS(vec_nr)
);
+DECLARE_EVENT_CLASS(tasklet,
+
+ TP_PROTO(struct tasklet_struct *t, void *func),
+
+ TP_ARGS(t, func),
+
+ TP_STRUCT__entry(
+ __field( void *, tasklet)
+ __field( void *, func)
+ ),
+
+ TP_fast_assign(
+ __entry->tasklet = t;
+ __entry->func = func;
+ ),
+
+ TP_printk("tasklet=%ps function=%ps", __entry->tasklet, __entry->func)
+);
+
+/**
+ * tasklet_entry - called immediately before the tasklet is run
+ * @t: tasklet pointer
+ * @func: tasklet callback or function being run
+ *
+ * Used to find individual tasklet execution time
+ */
+DEFINE_EVENT(tasklet, tasklet_entry,
+
+ TP_PROTO(struct tasklet_struct *t, void *func),
+
+ TP_ARGS(t, func)
+);
+
+/**
+ * tasklet_exit - called immediately after the tasklet is run
+ * @t: tasklet pointer
+ * @func: tasklet callback or function being run
+ *
+ * Used to find individual tasklet execution time
+ */
+DEFINE_EVENT(tasklet, tasklet_exit,
+
+ TP_PROTO(struct tasklet_struct *t, void *func),
+
+ TP_ARGS(t, func)
+);
+
#endif /* _TRACE_IRQ_H */
/* This part must be outside protection */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9ab5ca399a99..fadc6bbda27b 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -822,10 +822,15 @@ static void tasklet_action_common(struct softirq_action *a,
if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
if (tasklet_clear_sched(t)) {
- if (t->use_callback)
+ if (t->use_callback) {
+ trace_tasklet_entry(t, t->callback);
t->callback(t);
- else
+ trace_tasklet_exit(t, t->callback);
+ } else {
+ trace_tasklet_entry(t, t->func);
t->func(t->data);
+ trace_tasklet_exit(t, t->func);
+ }
}
tasklet_unlock(t);
continue;
--
2.43.0On Tue, 11 Nov 2025 21:16:20 -0600 Sumanth Gavini <sumanth.gavini@yahoo.com> wrote: > [elavila: Port to android-mainline] > [jstultz: Rebased to upstream, cut unused trace points, added > comments for the tracepoints, reworded commit] > > The intention is to keep the stable branch in sync with upstream fixes > and improve observability without introducing new functionality. > > Signed-off-by: Sumanth Gavini <sumanth.gavini@yahoo.com> I just noticed that this is being pulled into 6.1. I'm still not sure why this was added. Yes, it may improve observability, but that's because it is adding new functionality. Adding a trace event, is functionality and not a bug fix. I'm not going to argue against this backport, but I do want to point out that it is adding new functionality to a stable release. -- Steve
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