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, 148 insertions, 0 deletions

diff --git a/drivers/macintosh/windfarm_pid.c b/drivers/macintosh/windfarm_pid.c
new file mode 100644
index 000000000..bb31b0e93
--- /dev/null
+++ b/drivers/macintosh/windfarm_pid.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Windfarm PowerMac thermal control. Generic PID helpers
+ *
+ * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
+ *                    <benh@kernel.crashing.org>
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+#include "windfarm_pid.h"
+
+#undef DEBUG
+
+#ifdef DEBUG
+#define DBG(args...)	printk(args)
+#else
+#define DBG(args...)	do { } while(0)
+#endif
+
+void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param)
+{
+	memset(st, 0, sizeof(struct wf_pid_state));
+	st->param = *param;
+	st->first = 1;
+}
+EXPORT_SYMBOL_GPL(wf_pid_init);
+
+s32 wf_pid_run(struct wf_pid_state *st, s32 new_sample)
+{
+	s64	error, integ, deriv;
+	s32	target;
+	int	i, hlen = st->param.history_len;
+
+	/* Calculate error term */
+	error = new_sample - st->param.itarget;
+
+	/* Get samples into our history buffer */
+	if (st->first) {
+		for (i = 0; i < hlen; i++) {
+			st->samples[i] = new_sample;
+			st->errors[i] = error;
+		}
+		st->first = 0;
+		st->index = 0;
+	} else {
+		st->index = (st->index + 1) % hlen;
+		st->samples[st->index] = new_sample;
+		st->errors[st->index] = error;
+	}
+
+	/* Calculate integral term */
+	for (i = 0, integ = 0; i < hlen; i++)
+		integ += st->errors[(st->index + hlen - i) % hlen];
+	integ *= st->param.interval;
+
+	/* Calculate derivative term */
+	deriv = st->errors[st->index] -
+		st->errors[(st->index + hlen - 1) % hlen];
+	deriv /= st->param.interval;
+
+	/* Calculate target */
+	target = (s32)((integ * (s64)st->param.gr + deriv * (s64)st->param.gd +
+		  error * (s64)st->param.gp) >> 36);
+	if (st->param.additive)
+		target += st->target;
+	target = max(target, st->param.min);
+	target = min(target, st->param.max);
+	st->target = target;
+
+	return st->target;
+}
+EXPORT_SYMBOL_GPL(wf_pid_run);
+
+void wf_cpu_pid_init(struct wf_cpu_pid_state *st,
+		     struct wf_cpu_pid_param *param)
+{
+	memset(st, 0, sizeof(struct wf_cpu_pid_state));
+	st->param = *param;
+	st->first = 1;
+}
+EXPORT_SYMBOL_GPL(wf_cpu_pid_init);
+
+s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 new_power, s32 new_temp)
+{
+	s64	integ, deriv, prop;
+	s32	error, target, sval, adj;
+	int	i, hlen = st->param.history_len;
+
+	/* Calculate error term */
+	error = st->param.pmaxadj - new_power;
+
+	/* Get samples into our history buffer */
+	if (st->first) {
+		for (i = 0; i < hlen; i++) {
+			st->powers[i] = new_power;
+			st->errors[i] = error;
+		}
+		st->temps[0] = st->temps[1] = new_temp;
+		st->first = 0;
+		st->index = st->tindex = 0;
+	} else {
+		st->index = (st->index + 1) % hlen;
+		st->powers[st->index] = new_power;
+		st->errors[st->index] = error;
+		st->tindex = (st->tindex + 1) % 2;
+		st->temps[st->tindex] = new_temp;
+	}
+
+	/* Calculate integral term */
+	for (i = 0, integ = 0; i < hlen; i++)
+		integ += st->errors[(st->index + hlen - i) % hlen];
+	integ *= st->param.interval;
+	integ *= st->param.gr;
+	sval = st->param.tmax - (s32)(integ >> 20);
+	adj = min(st->param.ttarget, sval);
+
+	DBG("integ: %lx, sval: %lx, adj: %lx\n", integ, sval, adj);
+
+	/* Calculate derivative term */
+	deriv = st->temps[st->tindex] -
+		st->temps[(st->tindex + 2 - 1) % 2];
+	deriv /= st->param.interval;
+	deriv *= st->param.gd;
+
+	/* Calculate proportional term */
+	prop = st->last_delta = (new_temp - adj);
+	prop *= st->param.gp;
+
+	DBG("deriv: %lx, prop: %lx\n", deriv, prop);
+
+	/* Calculate target */
+	target = st->target + (s32)((deriv + prop) >> 36);
+	target = max(target, st->param.min);
+	target = min(target, st->param.max);
+	st->target = target;
+
+	return st->target;
+}
+EXPORT_SYMBOL_GPL(wf_cpu_pid_run);
+
+MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
+MODULE_DESCRIPTION("PID algorithm for PowerMacs thermal control");
+MODULE_LICENSE("GPL");