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afbe797317
As tracepoints are discouraged from being added in a header because it can cause side effects if other tracepoints are in headers, as well as bloat the kernel as the trace_<tracepoint>() function is not a small inline, the common workaround is to add a function call that calls a wrapper function in a C file that then calls the tracepoint. But as function calls add overhead, this function should only be called when the tracepoint in question is enabled. To get around this overhead, a static_branch can be used to only have the tracepoint wrapper get called when the tracepoint is enabled. Add a tracepoint_enabled(tp) macro that gets passed the name of the tracepoint, and this becomes a static_branch that is enabled when the tracepoint is enabled and is a nop when the tracepoint is disabled. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.