From: "Steven Rostedt (Red Hat)" If a function should be called before a tracepoint is enabled and/or after it is disabled, the TRACE_EVENT_FN() serves this purpose. But it is not well documented. Having it as a sample would help developers to know how to use it. Signed-off-by: Steven Rostedt --- samples/trace_events/trace-events-sample.c | 51 ++++++++++++++++++++++++++++++ samples/trace_events/trace-events-sample.h | 44 ++++++++++++++++++++++++++ 2 files changed, 95 insertions(+) diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index c396a49b5d78..39d4484aef53 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -49,6 +49,52 @@ static int simple_thread(void *arg) } static struct task_struct *simple_tsk; +static struct task_struct *simple_tsk_fn; + +static void simple_thread_func_fn(int cnt) +{ + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + + /* More silly tracepoints */ + trace_foo_bar_with_fn("Look at me", cnt); +} + +static int simple_thread_fn(void *arg) +{ + int cnt = 0; + + while (!kthread_should_stop()) + simple_thread_func_fn(cnt++); + + return 0; +} + +static DEFINE_MUTEX(thread_mutex); + +void foo_bar_reg(void) +{ + pr_info("Starting thread for foo_bar_fn\n"); + /* + * We shouldn't be able to start a trace when the module is + * unloading (there's other locks to prevent that). But + * for consistency sake, we still take the thread_mutex. + */ + mutex_lock(&thread_mutex); + simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn"); + mutex_unlock(&thread_mutex); +} + +void foo_bar_unreg(void) +{ + pr_info("Killing thread for foo_bar_fn\n"); + /* protect against module unloading */ + mutex_lock(&thread_mutex); + if (simple_tsk_fn) + kthread_stop(simple_tsk_fn); + simple_tsk_fn = NULL; + mutex_unlock(&thread_mutex); +} static int __init trace_event_init(void) { @@ -62,6 +108,11 @@ static int __init trace_event_init(void) static void __exit trace_event_exit(void) { kthread_stop(simple_tsk); + mutex_lock(&thread_mutex); + if (simple_tsk_fn) + kthread_stop(simple_tsk_fn); + simple_tsk_fn = NULL; + mutex_unlock(&thread_mutex); } module_init(trace_event_init); diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h index c3232340914d..d0be8411b527 100644 --- a/samples/trace_events/trace-events-sample.h +++ b/samples/trace_events/trace-events-sample.h @@ -270,6 +270,50 @@ TRACE_EVENT_CONDITION(foo_bar_with_cond, TP_printk("foo %s %d", __get_str(foo), __entry->bar) ); + +void foo_bar_reg(void); +void foo_bar_unreg(void); + +/* + * Now in the case that some function needs to be called when the + * tracepoint is enabled and/or when it is disabled, the + * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT() + * but adds two more parameters at the end: + * + * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg) + * + * reg and unreg are functions with the prototype of: + * + * void reg(void) + * + * The reg function gets called before the tracepoint is enabled, and + * the unreg function gets called after the tracepoint is disabled. + * + * Note, reg and unreg are allowed to be NULL. If you only need to + * call a function before enabling, or after disabling, just set one + * function and pass in NULL for the other parameter. + */ +TRACE_EVENT_FN(foo_bar_with_fn, + + TP_PROTO(const char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_STRUCT__entry( + __string( foo, foo ) + __field( int, bar ) + ), + + TP_fast_assign( + __assign_str(foo, foo); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __get_str(foo), __entry->bar), + + foo_bar_reg, foo_bar_unreg +); + #endif /***** NOTICE! The #if protection ends here. *****/ -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/