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>

2 files changed, 38 insertions, 0 deletions

diff --git a/arch/arc/plat-sim/Makefile b/arch/arc/plat-sim/Makefile
new file mode 100644
index 000000000..ea9389bf8
--- /dev/null
+++ b/arch/arc/plat-sim/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2011-2012 Synopsys, Inc. (www.synopsys.com)
+#
+
+obj-y := platform.o
diff --git a/arch/arc/plat-sim/platform.c b/arch/arc/plat-sim/platform.c
new file mode 100644
index 000000000..2bde2a6e3
--- /dev/null
+++ b/arch/arc/plat-sim/platform.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARC simulation Platform support code
+ *
+ * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
+ */
+
+#include <linux/init.h>
+#include <asm/mach_desc.h>
+
+/*----------------------- Machine Descriptions ------------------------------
+ *
+ * Machine description is simply a set of platform/board specific callbacks
+ * This is not directly related to DeviceTree based dynamic device creation,
+ * however as part of early device tree scan, we also select the right
+ * callback set, by matching the DT compatible name.
+ */
+
+static const char *simulation_compat[] __initconst = {
+#ifdef CONFIG_ISA_ARCOMPACT
+	"snps,nsim",
+	"snps,nsimosci",
+#else
+	"snps,nsimosci_hs",
+	"snps,zebu_hs",
+#endif
+	NULL,
+};
+
+MACHINE_START(SIMULATION, "simulation")
+	.dt_compat	= simulation_compat,
+MACHINE_END