[RFC][PATCH 00/10] tracing: Use TRACE_DEFINE_ENUM() to show enum values

Steven Rostedt
2015-03-27T21:38:21Z

As there are many tracepoints that use __print_symbolic() to translate
numbers into ASCII strings, and several of these translate enums as
well, it causes a problem for user space tools that read the tracepoint
format files and have to translate the binary data to their associated
strings.

For example, with the tlb_flush tracepoint, we have this in the format
file:

print fmt: "pages:%ld reason:%s (%d)", REC->pages,
__print_symbolic(REC->reason,
{ TLB_FLUSH_ON_TASK_SWITCH, "flush on task switch" },
{ TLB_REMOTE_SHOOTDOWN, "remote shootdown" },
{ TLB_LOCAL_SHOOTDOWN, "local shootdown" },
{ TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" }), REC->reason

Now, userspace does not know what the value of TLB_REMOTE_SHOOTDOWN is.
To solve this, a new macro is created as a helper to allow tracepoints
to export enums they use to userspace. This macro is called,
TRACE_DEFINE_ENUM(), such that

TRACE_DEFINE_ENUM(TLB_REMOTE_SHOOTDOWN);

Will export the TLB_REMOTE_SHOOTDOWN enum to use space.

How that is done is with a new file in the debugfs tracing directory.

# cat /sys/kernel/debug/tracing/enum_map
TLB_LOCAL_MM_SHOOTDOWN 3
TLB_LOCAL_SHOOTDOWN 2
TLB_REMOTE_SHOOTDOWN 1
TLB_FLUSH_ON_TASK_SWITCH 0

Now userspace, when seeing TLB_REMOTE_SHOOTDOWN in the format, knows
that represents "1", and can do the conversions properly.

Local SHA1: 6115e48a506e738f0f24771b4c87e4ba90d3d1c2

Steven Rostedt (Red Hat) (10):
tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values
tracing: Allow for modules to export their trace enums as well
x86/tlb/trace: Export enums in used by tlb_flush tracepoint
net/9p/tracing: Export enums in tracepoints to userspace
f2fs: Export the enums in the tracepoints to userspace
irq/tracing: Export enums in tracepoints to user space
mm: tracing: Export enums in tracepoints to user space
SUNRPC: Export enums in tracepoints to user space
v4l: Export enums used by tracepoints to user space
writeback: Export enums used by tracepoint to user space

----
include/asm-generic/vmlinux.lds.h | 5 +-
include/linux/module.h | 2 +
include/linux/tracepoint.h | 7 +
include/trace/events/9p.h | 157 +++++++++++++----------
include/trace/events/f2fs.h | 21 +++
include/trace/events/irq.h | 39 ++++--
include/trace/events/migrate.h | 42 ++++--
include/trace/events/sunrpc.h | 62 ++++++---
include/trace/events/tlb.h | 30 ++++-
include/trace/events/v4l2.h | 75 +++++++----
include/trace/events/writeback.h | 33 +++--
include/trace/ftrace.h | 11 ++
kernel/module.c | 3 +
kernel/trace/trace.c | 260 +++++++++++++++++++++++++++++++++++++-
14 files changed, 598 insertions(+), 149 deletions(-)