context_tracking: User/kernel broundary cross trace events
This can be useful to track all kernel/user round trips.
And it's also helpful to debug the context tracking subsystem.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
diff --git a/include/trace/events/context_tracking.h b/include/trace/events/context_tracking.h
new file mode 100644
index 0000000..ce8007c
--- /dev/null
+++ b/include/trace/events/context_tracking.h
@@ -0,0 +1,58 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM context_tracking
+
+#if !defined(_TRACE_CONTEXT_TRACKING_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_CONTEXT_TRACKING_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(context_tracking_user,
+
+ TP_PROTO(int dummy),
+
+ TP_ARGS(dummy),
+
+ TP_STRUCT__entry(
+ __field( int, dummy )
+ ),
+
+ TP_fast_assign(
+ __entry->dummy = dummy;
+ ),
+
+ TP_printk("%s", "")
+);
+
+/**
+ * user_enter - called when the kernel resumes to userspace
+ * @dummy: dummy arg to make trace event macro happy
+ *
+ * This event occurs when the kernel resumes to userspace after
+ * an exception or a syscall.
+ */
+DEFINE_EVENT(context_tracking_user, user_enter,
+
+ TP_PROTO(int dummy),
+
+ TP_ARGS(dummy)
+);
+
+/**
+ * user_exit - called when userspace enters the kernel
+ * @dummy: dummy arg to make trace event macro happy
+ *
+ * This event occurs when userspace enters the kernel through
+ * an exception or a syscall.
+ */
+DEFINE_EVENT(context_tracking_user, user_exit,
+
+ TP_PROTO(int dummy),
+
+ TP_ARGS(dummy)
+);
+
+
+#endif /* _TRACE_CONTEXT_TRACKING_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index c178226..247091b 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -20,6 +20,9 @@
#include <linux/hardirq.h>
#include <linux/export.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/context_tracking.h>
+
struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE;
EXPORT_SYMBOL_GPL(context_tracking_enabled);
@@ -64,6 +67,7 @@
local_irq_save(flags);
if ( __this_cpu_read(context_tracking.state) != IN_USER) {
if (__this_cpu_read(context_tracking.active)) {
+ trace_user_enter(0);
/*
* At this stage, only low level arch entry code remains and
* then we'll run in userspace. We can assume there won't be
@@ -159,6 +163,7 @@
*/
rcu_user_exit();
vtime_user_exit(current);
+ trace_user_exit(0);
}
__this_cpu_write(context_tracking.state, IN_KERNEL);
}