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;