tracing: add __print_flags for events
Developers have been asking for the ability in the ftrace event tracer
to display names of bits in a flags variable.
Instead of printing out c2, it would be easier to read FOO|BAR|GOO,
assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7.
Some examples where this would be useful are the state flags in a context
switch, kmalloc flags, and even permision flags in accessing files.
[
v2 changes include:
Frederic Weisbecker's idea of using a mask instead of bits,
thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS.
Li Zefan's idea of allowing the caller of __print_flags to add their
own delimiter (or no delimiter) where we can get for file permissions
rwx instead of r|w|x.
]
[
v3 changes:
Christoph Hellwig's idea of using an array instead of va_args.
]
[ Impact: better displaying of flags in trace output ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index bae51dd..4b58cf1 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -3,12 +3,23 @@
#include <linux/trace_seq.h>
#include <linux/ring_buffer.h>
-
+#include <linux/percpu.h>
struct trace_array;
struct tracer;
struct dentry;
+DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
+
+struct trace_print_flags {
+ unsigned long mask;
+ const char *name;
+};
+
+const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
+ unsigned long flags,
+ const struct trace_print_flags *flag_array);
+
/*
* The trace entry - the most basic unit of tracing. This is what
* is printed in the end as a single line in the trace output, such as: