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Diffstat (limited to 'Documentation/trace/tracepoints.rst')
| -rw-r--r-- | Documentation/trace/tracepoints.rst | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/trace/tracepoints.rst b/Documentation/trace/tracepoints.rst index 6e3ce3bf3593..0cb8d9ca3d60 100644 --- a/Documentation/trace/tracepoints.rst +++ b/Documentation/trace/tracepoints.rst @@ -146,3 +146,30 @@ with jump labels and avoid conditional branches. define tracepoints. Check http://lwn.net/Articles/379903, http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362 for a series of articles with more details. + +If you require calling a tracepoint from a header file, it is not +recommended to call one directly or to use the trace_<tracepoint>_enabled() +function call, as tracepoints in header files can have side effects if a +header is included from a file that has CREATE_TRACE_POINTS set, as +well as the trace_<tracepoint>() is not that small of an inline +and can bloat the kernel if used by other inlined functions. Instead, +include tracepoint-defs.h and use tracepoint_enabled(). + +In a C file:: + + void do_trace_foo_bar_wrapper(args) + { + trace_foo_bar(args); + } + +In the header file:: + + DECLARE_TRACEPOINT(foo_bar); + + static inline void some_inline_function() + { + [..] + if (tracepoint_enabled(foo_bar)) + do_trace_foo_bar_wrapper(args); + [..] + } |