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/trace/ftrace.h b/include/trace/ftrace.h
index b5ff2e8..22c9471 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -87,6 +87,7 @@
* struct trace_seq *s = &iter->seq;
* struct ftrace_raw_<call> *field; <-- defined in stage 1
* struct trace_entry *entry;
+ * struct trace_seq *p;
* int ret;
*
* entry = iter->ent;
@@ -98,7 +99,9 @@
*
* field = (typeof(field))entry;
*
+ * p = get_cpu_var(ftrace_event_seq);
* ret = trace_seq_printf(s, <TP_printk> "\n");
+ * put_cpu();
* if (!ret)
* return TRACE_TYPE_PARTIAL_LINE;
*
@@ -119,6 +122,14 @@
#undef __get_str
#define __get_str(field) ((char *)__entry + __entry->__str_loc_##field)
+#undef __print_flags
+#define __print_flags(flag, delim, flag_array...) \
+ ({ \
+ static const struct trace_print_flags flags[] = \
+ { flag_array, { -1, NULL }}; \
+ ftrace_print_flags_seq(p, delim, flag, flags); \
+ })
+
#undef TRACE_EVENT
#define TRACE_EVENT(call, proto, args, tstruct, assign, print) \
enum print_line_t \
@@ -127,6 +138,7 @@
struct trace_seq *s = &iter->seq; \
struct ftrace_raw_##call *field; \
struct trace_entry *entry; \
+ struct trace_seq *p; \
int ret; \
\
entry = iter->ent; \
@@ -138,7 +150,9 @@
\
field = (typeof(field))entry; \
\
+ p = &get_cpu_var(ftrace_event_seq); \
ret = trace_seq_printf(s, #call ": " print); \
+ put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
