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, 216 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-econet-en751221.c b/drivers/clocksource/timer-econet-en751221.c
new file mode 100644
index 000000000..4008076b1
--- /dev/null
+++ b/drivers/clocksource/timer-econet-en751221.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Timer present on EcoNet EN75xx MIPS based SoCs.
+ *
+ * Copyright (C) 2025 by Caleb James DeLisle <cjd@cjdns.fr>
+ */
+
+#include <linux/io.h>
+#include <linux/cpumask.h>
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/sched_clock.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/cpuhotplug.h>
+#include <linux/clk.h>
+
+#define ECONET_BITS			32
+#define ECONET_MIN_DELTA		0x00001000
+#define ECONET_MAX_DELTA		GENMASK(ECONET_BITS - 2, 0)
+/* 34Kc hardware has 1 block and 1004Kc has 2. */
+#define ECONET_NUM_BLOCKS		DIV_ROUND_UP(NR_CPUS, 2)
+
+static struct {
+	void __iomem	*membase[ECONET_NUM_BLOCKS];
+	u32		freq_hz;
+} econet_timer __ro_after_init;
+
+static DEFINE_PER_CPU(struct clock_event_device, econet_timer_pcpu);
+
+/* Each memory block has 2 timers, the order of registers is:
+ * CTL, CMR0, CNT0, CMR1, CNT1
+ */
+static inline void __iomem *reg_ctl(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1];
+}
+
+static inline void __iomem *reg_compare(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1] + (timer_n & 1) * 0x08 + 0x04;
+}
+
+static inline void __iomem *reg_count(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1] + (timer_n & 1) * 0x08 + 0x08;
+}
+
+static inline u32 ctl_bit_enabled(u32 timer_n)
+{
+	return 1U << (timer_n & 1);
+}
+
+static inline u32 ctl_bit_pending(u32 timer_n)
+{
+	return 1U << ((timer_n & 1) + 16);
+}
+
+static bool cevt_is_pending(int cpu_id)
+{
+	return ioread32(reg_ctl(cpu_id)) & ctl_bit_pending(cpu_id);
+}
+
+static irqreturn_t cevt_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *dev = this_cpu_ptr(&econet_timer_pcpu);
+	int cpu = cpumask_first(dev->cpumask);
+
+	/* Each VPE has its own events,
+	 * so this will only happen on spurious interrupt.
+	 */
+	if (!cevt_is_pending(cpu))
+		return IRQ_NONE;
+
+	iowrite32(ioread32(reg_count(cpu)), reg_compare(cpu));
+	dev->event_handler(dev);
+	return IRQ_HANDLED;
+}
+
+static int cevt_set_next_event(ulong delta, struct clock_event_device *dev)
+{
+	u32 next;
+	int cpu;
+
+	cpu = cpumask_first(dev->cpumask);
+	next = ioread32(reg_count(cpu)) + delta;
+	iowrite32(next, reg_compare(cpu));
+
+	if ((s32)(next - ioread32(reg_count(cpu))) < ECONET_MIN_DELTA / 2)
+		return -ETIME;
+
+	return 0;
+}
+
+static int cevt_init_cpu(uint cpu)
+{
+	struct clock_event_device *cd = &per_cpu(econet_timer_pcpu, cpu);
+	u32 reg;
+
+	pr_debug("%s: Setting up clockevent for CPU %d\n", cd->name, cpu);
+
+	reg = ioread32(reg_ctl(cpu)) | ctl_bit_enabled(cpu);
+	iowrite32(reg, reg_ctl(cpu));
+
+	enable_percpu_irq(cd->irq, IRQ_TYPE_NONE);
+
+	/* Do this last because it synchronously configures the timer */
+	clockevents_config_and_register(cd, econet_timer.freq_hz,
+					ECONET_MIN_DELTA, ECONET_MAX_DELTA);
+
+	return 0;
+}
+
+static u64 notrace sched_clock_read(void)
+{
+	/* Always read from clock zero no matter the CPU */
+	return (u64)ioread32(reg_count(0));
+}
+
+/* Init */
+
+static void __init cevt_dev_init(uint cpu)
+{
+	iowrite32(0, reg_count(cpu));
+	iowrite32(U32_MAX, reg_compare(cpu));
+}
+
+static int __init cevt_init(struct device_node *np)
+{
+	int i, irq, ret;
+
+	irq = irq_of_parse_and_map(np, 0);
+	if (irq <= 0) {
+		pr_err("%pOFn: irq_of_parse_and_map failed", np);
+		return -EINVAL;
+	}
+
+	ret = request_percpu_irq(irq, cevt_interrupt, np->name, &econet_timer_pcpu);
+
+	if (ret < 0) {
+		pr_err("%pOFn: IRQ %d setup failed (%d)\n", np, irq, ret);
+		goto err_unmap_irq;
+	}
+
+	for_each_possible_cpu(i) {
+		struct clock_event_device *cd = &per_cpu(econet_timer_pcpu, i);
+
+		cd->rating		= 310;
+		cd->features		= CLOCK_EVT_FEAT_ONESHOT |
+					  CLOCK_EVT_FEAT_C3STOP |
+					  CLOCK_EVT_FEAT_PERCPU;
+		cd->set_next_event	= cevt_set_next_event;
+		cd->irq			= irq;
+		cd->cpumask		= cpumask_of(i);
+		cd->name		= np->name;
+
+		cevt_dev_init(i);
+	}
+
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+			  "clockevents/econet/timer:starting",
+			  cevt_init_cpu, NULL);
+	return 0;
+
+err_unmap_irq:
+	irq_dispose_mapping(irq);
+	return ret;
+}
+
+static int __init timer_init(struct device_node *np)
+{
+	int num_blocks = DIV_ROUND_UP(num_possible_cpus(), 2);
+	struct clk *clk;
+	int ret;
+
+	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		pr_err("%pOFn: Failed to get CPU clock from DT %ld\n", np, PTR_ERR(clk));
+		return PTR_ERR(clk);
+	}
+
+	econet_timer.freq_hz = clk_get_rate(clk);
+
+	for (int i = 0; i < num_blocks; i++) {
+		econet_timer.membase[i] = of_iomap(np, i);
+		if (!econet_timer.membase[i]) {
+			pr_err("%pOFn: failed to map register [%d]\n", np, i);
+			return -ENXIO;
+		}
+	}
+
+	/* For clocksource purposes always read clock zero, whatever the CPU */
+	ret = clocksource_mmio_init(reg_count(0), np->name,
+				    econet_timer.freq_hz, 301, ECONET_BITS,
+				    clocksource_mmio_readl_up);
+	if (ret) {
+		pr_err("%pOFn: clocksource_mmio_init failed: %d", np, ret);
+		return ret;
+	}
+
+	ret = cevt_init(np);
+	if (ret < 0)
+		return ret;
+
+	sched_clock_register(sched_clock_read, ECONET_BITS,
+			     econet_timer.freq_hz);
+
+	pr_info("%pOFn: using %u.%03u MHz high precision timer\n", np,
+		econet_timer.freq_hz / 1000000,
+		(econet_timer.freq_hz / 1000) % 1000);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(econet_timer_hpt, "econet,en751221-timer", timer_init);