ftrace: deprecate disabling via ftrace_enabled sysctl

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Writing 0 to kernel.ftrace_enabled has not reliably disabled ftrace
for years (FTRACE_OPS_FL_PERMANENT users already block it, and more
callers rely on ftrace always being on). Refuse the write instead of
leaving it in an inconsistent "disables some, not all" state: return
-EOPNOTSUPP and log a message. Reads and enabling (writing 1) are
unaffected.

Update the docs to note the deprecation up front.

Link: https://patch.msgid.link/20260806153000.4184871-2-andrey.grodzovsky@crowdstrike.com
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

...

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Andrey Grodzovsky 2026-08-06 11:29:59 -04:00 • committed by Steven Rostedt

parent 075b74841b

commit b0c8570491

2 changed files with 11 additions and 37 deletions

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5

Documentation/trace/ftrace.rst

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43

kernel/trace/ftrace.c

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