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, 118 insertions, 0 deletions

diff --git a/arch/mips/econet/init.c b/arch/mips/econet/init.c
new file mode 100644
index 000000000..ae45b8788
--- /dev/null
+++ b/arch/mips/econet/init.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * EcoNet setup code
+ *
+ * Copyright (C) 2025 Caleb James DeLisle <cjd@cjdns.fr>
+ */
+
+#include <linux/init.h>
+#include <linux/of_clk.h>
+#include <linux/irqchip.h>
+
+#include <asm/addrspace.h>
+#include <asm/io.h>
+#include <asm/bootinfo.h>
+#include <asm/time.h>
+#include <asm/prom.h>
+#include <asm/smp-ops.h>
+#include <asm/reboot.h>
+
+#define CR_AHB_RSTCR		((void __iomem *)CKSEG1ADDR(0x1fb00040))
+#define RESET			BIT(31)
+
+#define UART_BASE		CKSEG1ADDR(0x1fbf0003)
+#define UART_REG_SHIFT		2
+
+static void hw_reset(char *command)
+{
+	iowrite32(RESET, CR_AHB_RSTCR);
+}
+
+/*
+ * vsmp_init_secondary expects either GIC or cascading interrupt configuration.
+ * The EN751221 is a 34Kc with VEIC, but not GIC compatible. The cascading
+ * configuration enables lines 6 and 7 for performance counters, but when this
+ * is done on the EN751221 intc with VEIC enabled, it causes the whole intc to
+ * stop sending interrupts.
+ * Only unmask lines 0 and 1 (software interrupts) in init_secondary.
+ */
+#ifdef CONFIG_MIPS_MT_SMP
+extern const struct plat_smp_ops vsmp_smp_ops;
+static struct plat_smp_ops en75_smp_ops __ro_after_init;
+
+static void en751221_init_secondary(void)
+{
+	write_c0_status((read_c0_status() & ~ST0_IM) |
+		(STATUSF_IP0 | STATUSF_IP1));
+}
+
+static int __init en751221_register_vsmp_smp_ops(void)
+{
+	if (!cpu_has_mipsmt)
+		return -ENODEV;
+
+	en75_smp_ops = vsmp_smp_ops;
+	en75_smp_ops.init_secondary = en751221_init_secondary;
+	register_smp_ops(&en75_smp_ops);
+	return 0;
+}
+#else
+static int __init en751221_register_vsmp_smp_ops(void)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_MIPS_MT_SMP */
+
+/* 1. Bring up early printk. */
+void __init prom_init(void)
+{
+	setup_8250_early_printk_port(UART_BASE, UART_REG_SHIFT, 0);
+	_machine_restart = hw_reset;
+}
+
+/* 2. Parse the DT and find memory */
+void __init plat_mem_setup(void)
+{
+	void *dtb;
+
+	set_io_port_base(KSEG1);
+
+	dtb = get_fdt();
+	if (!dtb)
+		panic("no dtb found");
+
+	__dt_setup_arch(dtb);
+
+	early_init_dt_scan_memory();
+}
+
+/* 3. Overload __weak device_tree_init(), add SMP ops */
+void __init device_tree_init(void)
+{
+	unflatten_and_copy_device_tree();
+
+	/* EN751221 dual-vpe */
+	if (!en751221_register_vsmp_smp_ops())
+		return;
+
+	/* EN751221 with MT_SMP disabled */
+	register_up_smp_ops();
+}
+
+const char *get_system_type(void)
+{
+	return "EcoNet-EN75xx";
+}
+
+/* 4. Initialize the IRQ subsystem */
+void __init arch_init_irq(void)
+{
+	irqchip_init();
+}
+
+/* 5. Timers */
+void __init plat_time_init(void)
+{
+	of_clk_init(NULL);
+	timer_probe();
+}