tracing: Have the reg function allow to fail

Some tracepoints have a registration function that gets enabled when the
tracepoint is enabled. There may be cases that the registraction function
must fail (for example, can't allocate enough memory). In this case, the
tracepoint should also fail to register, otherwise the user would not know
why the tracepoint is not working.

Cc: David Howells <dhowells@redhat.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

15 files changed, 34 insertions, 20 deletions

diff --git a/arch/powerpc/include/asm/trace.h b/arch/powerpc/include/asm/trace.h
index 32e36b16773f..c05cef6ee06c 100644
--- a/arch/powerpc/include/asm/trace.h
+++ b/arch/powerpc/include/asm/trace.h
@@ -54,7 +54,7 @@ DEFINE_EVENT(ppc64_interrupt_class, timer_interrupt_exit,
 );
 
 #ifdef CONFIG_PPC_PSERIES
-extern void hcall_tracepoint_regfunc(void);
+extern int hcall_tracepoint_regfunc(void);
 extern void hcall_tracepoint_unregfunc(void);
 
 TRACE_EVENT_FN_COND(hcall_entry,
@@ -104,7 +104,7 @@ TRACE_EVENT_FN_COND(hcall_exit,
 #endif
 
 #ifdef CONFIG_PPC_POWERNV
-extern void opal_tracepoint_regfunc(void);
+extern int opal_tracepoint_regfunc(void);
 extern void opal_tracepoint_unregfunc(void);
 
 TRACE_EVENT_FN(opal_entry,
diff --git a/arch/powerpc/platforms/powernv/opal-tracepoints.c b/arch/powerpc/platforms/powernv/opal-tracepoints.c
index 1e496b780efd..3c447002edff 100644
--- a/arch/powerpc/platforms/powernv/opal-tracepoints.c
+++ b/arch/powerpc/platforms/powernv/opal-tracepoints.c
@@ -6,9 +6,10 @@
 #ifdef HAVE_JUMP_LABEL
 struct static_key opal_tracepoint_key = STATIC_KEY_INIT;
 
-void opal_tracepoint_regfunc(void)
+int opal_tracepoint_regfunc(void)
 {
 	static_key_slow_inc(&opal_tracepoint_key);
+	return 0;
 }
 
 void opal_tracepoint_unregfunc(void)
@@ -25,9 +26,10 @@ void opal_tracepoint_unregfunc(void)
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 extern long opal_tracepoint_refcount;
 
-void opal_tracepoint_regfunc(void)
+int opal_tracepoint_regfunc(void)
 {
 	opal_tracepoint_refcount++;
+	return 0;
 }
 
 void opal_tracepoint_unregfunc(void)
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index aa35245d8d6d..c0423ce3955c 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -661,9 +661,10 @@ EXPORT_SYMBOL(arch_free_page);
 #ifdef HAVE_JUMP_LABEL
 struct static_key hcall_tracepoint_key = STATIC_KEY_INIT;
 
-void hcall_tracepoint_regfunc(void)
+int hcall_tracepoint_regfunc(void)
 {
 	static_key_slow_inc(&hcall_tracepoint_key);
+	return 0;
 }
 
 void hcall_tracepoint_unregfunc(void)
@@ -680,9 +681,10 @@ void hcall_tracepoint_unregfunc(void)
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 extern long hcall_tracepoint_refcount;
 
-void hcall_tracepoint_regfunc(void)
+int hcall_tracepoint_regfunc(void)
 {
 	hcall_tracepoint_refcount++;
+	return 0;
 }
 
 void hcall_tracepoint_unregfunc(void)
diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h
index 2fbc66c7885b..2422b14c50a7 100644
--- a/arch/x86/include/asm/trace/exceptions.h
+++ b/arch/x86/include/asm/trace/exceptions.h
@@ -6,7 +6,7 @@
 
 #include <linux/tracepoint.h>
 
-extern void trace_irq_vector_regfunc(void);
+extern int trace_irq_vector_regfunc(void);
 extern void trace_irq_vector_unregfunc(void);
 
 DECLARE_EVENT_CLASS(x86_exceptions,
diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
index 38a09a13a9bc..32dd6a9e343c 100644
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -6,7 +6,7 @@
 
 #include <linux/tracepoint.h>
 
-extern void trace_irq_vector_regfunc(void);
+extern int trace_irq_vector_regfunc(void);
 extern void trace_irq_vector_unregfunc(void);
 
 DECLARE_EVENT_CLASS(x86_irq_vector,
diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
index 1c113db9ed57..15515132bf0d 100644
--- a/arch/x86/kernel/tracepoint.c
+++ b/arch/x86/kernel/tracepoint.c
@@ -34,7 +34,7 @@ static void switch_idt(void *arg)
 	local_irq_restore(flags);
 }
 
-void trace_irq_vector_regfunc(void)
+int trace_irq_vector_regfunc(void)
 {
 	mutex_lock(&irq_vector_mutex);
 	if (!trace_irq_vector_refcount) {
@@ -44,6 +44,7 @@ void trace_irq_vector_regfunc(void)
 	}
 	trace_irq_vector_refcount++;
 	mutex_unlock(&irq_vector_mutex);
+	return 0;
 }
 
 void trace_irq_vector_unregfunc(void)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index b432b64e307a..6a2b995d7fc4 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -77,9 +77,10 @@ static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);
 static struct static_key i2c_trace_msg = STATIC_KEY_INIT_FALSE;
 static bool is_registered;
 
-void i2c_transfer_trace_reg(void)
+int i2c_transfer_trace_reg(void)
 {
 	static_key_slow_inc(&i2c_trace_msg);
+	return 0;
 }
 
 void i2c_transfer_trace_unreg(void)
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 4ac89acb6136..a03192052066 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -29,7 +29,7 @@ struct tracepoint_func {
 struct tracepoint {
 	const char *name;		/* Tracepoint name */
 	struct static_key key;
-	void (*regfunc)(void);
+	int (*regfunc)(void);
 	void (*unregfunc)(void);
 	struct tracepoint_func __rcu *funcs;
 };
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index be586c632a0c..f72fcfe0e66a 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -81,7 +81,7 @@ static inline void tracepoint_synchronize_unregister(void)
 }
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
-extern void syscall_regfunc(void);
+extern int syscall_regfunc(void);
 extern void syscall_unregfunc(void);
 #endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
 
diff --git a/include/trace/events/i2c.h b/include/trace/events/i2c.h
index fe17187df65d..4abb8eab34d3 100644
--- a/include/trace/events/i2c.h
+++ b/include/trace/events/i2c.h
@@ -20,7 +20,7 @@
 /*
  * drivers/i2c/i2c-core.c
  */
-extern void i2c_transfer_trace_reg(void);
+extern int i2c_transfer_trace_reg(void);
 extern void i2c_transfer_trace_unreg(void);
 
 /*
diff --git a/kernel/trace/trace_benchmark.c b/kernel/trace/trace_benchmark.c
index 0f109c4130d3..f76d0416dd83 100644
--- a/kernel/trace/trace_benchmark.c
+++ b/kernel/trace/trace_benchmark.c
@@ -164,11 +164,12 @@ static int benchmark_event_kthread(void *arg)
  * When the benchmark tracepoint is enabled, it calls this
  * function and the thread that calls the tracepoint is created.
  */
-void trace_benchmark_reg(void)
+int trace_benchmark_reg(void)
 {
 	bm_event_thread = kthread_run(benchmark_event_kthread,
 				      NULL, "event_benchmark");
 	WARN_ON(!bm_event_thread);
+	return 0;
 }
 
 /*
diff --git a/kernel/trace/trace_benchmark.h b/kernel/trace/trace_benchmark.h
index 3c1df1df4e29..ebdbfc2f2a64 100644
--- a/kernel/trace/trace_benchmark.h
+++ b/kernel/trace/trace_benchmark.h
@@ -6,7 +6,7 @@
 
 #include <linux/tracepoint.h>
 
-extern void trace_benchmark_reg(void);
+extern int trace_benchmark_reg(void);
 extern void trace_benchmark_unreg(void);
 
 #define BENCHMARK_EVENT_STRLEN		128
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d0639d917899..1f9a31f934a4 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -194,9 +194,13 @@ static int tracepoint_add_func(struct tracepoint *tp,
 			       struct tracepoint_func *func, int prio)
 {
 	struct tracepoint_func *old, *tp_funcs;
+	int ret;
 
-	if (tp->regfunc && !static_key_enabled(&tp->key))
-		tp->regfunc();
+	if (tp->regfunc && !static_key_enabled(&tp->key)) {
+		ret = tp->regfunc();
+		if (ret < 0)
+			return ret;
+	}
 
 	tp_funcs = rcu_dereference_protected(tp->funcs,
 			lockdep_is_held(&tracepoints_mutex));
@@ -529,7 +533,7 @@ EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 static int sys_tracepoint_refcount;
 
-void syscall_regfunc(void)
+int syscall_regfunc(void)
 {
 	struct task_struct *p, *t;
 
@@ -541,6 +545,8 @@ void syscall_regfunc(void)
 		read_unlock(&tasklist_lock);
 	}
 	sys_tracepoint_refcount++;
+
+	return 0;
 }
 
 void syscall_unregfunc(void)
diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c
index 880a7d1d27d2..30e282d33d4d 100644
--- a/samples/trace_events/trace-events-sample.c
+++ b/samples/trace_events/trace-events-sample.c
@@ -79,7 +79,7 @@ static int simple_thread_fn(void *arg)
 
 static DEFINE_MUTEX(thread_mutex);
 
-void foo_bar_reg(void)
+int foo_bar_reg(void)
 {
 	pr_info("Starting thread for foo_bar_fn\n");
 	/*
@@ -90,6 +90,7 @@ void foo_bar_reg(void)
 	mutex_lock(&thread_mutex);
 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
 	mutex_unlock(&thread_mutex);
+	return 0;
 }
 
 void foo_bar_unreg(void)
diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index d6b75bb495b3..76a75ab7a608 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -354,7 +354,7 @@ TRACE_EVENT_CONDITION(foo_bar_with_cond,
 	TP_printk("foo %s %d", __get_str(foo), __entry->bar)
 );
 
-void foo_bar_reg(void);
+int foo_bar_reg(void);
 void foo_bar_unreg(void);
 
 /*