Steven Rostedt (Google) bd604f3db4 ftrace: Avoid needless updates of the ftrace function call
Song Shuai reported:

    The list func (ftrace_ops_list_func) will be patched first
    before the transition between old and new calls are set,
    which fixed the race described in this commit `59338f75`.

    While ftrace_trace_function changes from the list func to a
    ftrace_ops func, like unregistering the klp_ops to leave the only
    global_ops in ftrace_ops_list, the ftrace_[regs]_call will be
    replaced with the list func although it already exists. So there
    should be a condition to avoid this.

And suggested using another variable to keep track of what the ftrace
function is set to. But this could be simplified by using a helper
function that does the same with a static variable.

Link: https://lore.kernel.org/lkml/20221026132039.2236233-1-suagrfillet@gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221122180905.737b6f52@gandalf.local.home

Reported-by: Song Shuai <suagrfillet@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2022-11-23 19:08:31 -05:00
2022-11-20 16:02:16 -08:00

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.
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