ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 96 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf.txt b/tools/perf/Documentation/perf.txt
new file mode 100644
index 000000000..cbcc2e4d5
--- /dev/null
+++ b/tools/perf/Documentation/perf.txt
@@ -0,0 +1,96 @@
+perf(1)
+=======
+
+NAME
+----
+perf - Performance analysis tools for Linux
+
+SYNOPSIS
+--------
+[verse]
+'perf' [--version] [--help] [OPTIONS] COMMAND [ARGS]
+
+OPTIONS
+-------
+-h::
+--help::
+        Run perf help command.
+
+-v::
+--version::
+        Display perf version.
+
+-vv::
+        Print the compiled-in status of libraries.
+
+--exec-path::
+        Display or set exec path.
+
+--html-path::
+        Display html documentation path.
+
+-p::
+--paginate::
+        Set up pager.
+
+--no-pager::
+        Do not set pager.
+
+--buildid-dir::
+        Setup buildid cache directory. It has higher priority
+        than buildid.dir config file option.
+
+--list-cmds::
+        List the most commonly used perf commands.
+
+--list-opts::
+        List available perf options.
+
+--debugfs-dir::
+        Set debugfs directory or set environment variable PERF_DEBUGFS_DIR.
+
+--debug::
+        Setup debug variable (see list below) in value
+        range (0, 10). Use like:
+          --debug verbose   # sets verbose = 1
+          --debug verbose=2 # sets verbose = 2
+
+        List of debug variables allowed to set:
+          verbose          - general debug messages
+          ordered-events   - ordered events object debug messages
+          data-convert     - data convert command debug messages
+          stderr           - write debug output (option -v) to stderr
+                             in browser mode
+          perf-event-open  - Print perf_event_open() arguments and
+                             return value
+          kmaps            - Print kernel and module maps (perf script
+                             and perf report without browser)
+
+--debug-file::
+	Write debug output to a specified file.
+
+DESCRIPTION
+-----------
+Performance counters for Linux are a new kernel-based subsystem
+that provide a framework for all things performance analysis. It
+covers hardware level (CPU/PMU, Performance Monitoring Unit) features
+and software features (software counters, tracepoints) as well.
+
+SEE ALSO
+--------
+linkperf:perf-stat[1], linkperf:perf-top[1],
+linkperf:perf-record[1], linkperf:perf-report[1],
+linkperf:perf-list[1]
+
+linkperf:perf-amd-ibs[1], linkperf:perf-annotate[1],
+linkperf:perf-archive[1], linkperf:perf-arm-spe[1],
+linkperf:perf-bench[1], linkperf:perf-buildid-cache[1],
+linkperf:perf-buildid-list[1], linkperf:perf-c2c[1],
+linkperf:perf-config[1], linkperf:perf-data[1], linkperf:perf-diff[1],
+linkperf:perf-evlist[1], linkperf:perf-ftrace[1],
+linkperf:perf-help[1], linkperf:perf-inject[1],
+linkperf:perf-intel-pt[1], linkperf:perf-iostat[1], linkperf:perf-kallsyms[1],
+linkperf:perf-kmem[1], linkperf:perf-kvm[1], linkperf:perf-lock[1],
+linkperf:perf-mem[1], linkperf:perf-probe[1], linkperf:perf-sched[1],
+linkperf:perf-script[1], linkperf:perf-test[1],
+linkperf:perf-trace[1], linkperf:perf-version[1]