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, 90 insertions, 0 deletions

diff --git a/arch/m68k/mac/baboon.c b/arch/m68k/mac/baboon.c
new file mode 100644
index 000000000..5c97a7058
--- /dev/null
+++ b/arch/m68k/mac/baboon.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Baboon Custom IC Management
+ *
+ * The Baboon custom IC controls the IDE, PCMCIA and media bay on the
+ * PowerBook 190. It multiplexes multiple interrupt sources onto the
+ * Nubus slot $C interrupt.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/irq.h>
+
+#include <asm/macintosh.h>
+#include <asm/macints.h>
+#include <asm/mac_baboon.h>
+
+#include "mac.h"
+
+int baboon_present;
+static volatile struct baboon *baboon;
+
+/*
+ * Baboon initialization.
+ */
+
+void __init baboon_init(void)
+{
+	if (macintosh_config->ident != MAC_MODEL_PB190) {
+		baboon = NULL;
+		baboon_present = 0;
+		return;
+	}
+
+	baboon = (struct baboon *) BABOON_BASE;
+	baboon_present = 1;
+
+	pr_debug("Baboon detected at %p\n", baboon);
+}
+
+/*
+ * Baboon interrupt handler.
+ * XXX how do you clear a pending IRQ? is it even necessary?
+ */
+
+static void baboon_irq(struct irq_desc *desc)
+{
+	short events, irq_bit;
+	int irq_num;
+
+	events = baboon->mb_ifr & 0x07;
+	irq_num = IRQ_BABOON_0;
+	irq_bit = 1;
+	do {
+		if (events & irq_bit) {
+			events &= ~irq_bit;
+			generic_handle_irq(irq_num);
+		}
+		++irq_num;
+		irq_bit <<= 1;
+	} while (events);
+}
+
+/*
+ * Register the Baboon interrupt dispatcher on nubus slot $C.
+ */
+
+void __init baboon_register_interrupts(void)
+{
+	irq_set_chained_handler(IRQ_NUBUS_C, baboon_irq);
+}
+
+/*
+ * The means for masking individual Baboon interrupts remains a mystery.
+ * However, since we only use the IDE IRQ, we can just enable/disable all
+ * Baboon interrupts. If/when we handle more than one Baboon IRQ, we must
+ * either figure out how to mask them individually or else implement the
+ * same workaround that's used for NuBus slots (see nubus_disabled and
+ * via_nubus_irq_shutdown).
+ */
+
+void baboon_irq_enable(int irq)
+{
+	mac_irq_enable(irq_get_irq_data(IRQ_NUBUS_C));
+}
+
+void baboon_irq_disable(int irq)
+{
+	mac_irq_disable(irq_get_irq_data(IRQ_NUBUS_C));
+}