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, 154 insertions, 0 deletions

diff --git a/arch/mips/sgi-ip27/ip27-timer.c b/arch/mips/sgi-ip27/ip27-timer.c
new file mode 100644
index 000000000..5f4da05cb
--- /dev/null
+++ b/arch/mips/sgi-ip27/ip27-timer.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1999, 2000, 05, 06 Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
+ */
+#include <linux/bcd.h>
+#include <linux/clockchips.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched_clock.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/param.h>
+#include <linux/smp.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/mm.h>
+#include <linux/platform_device.h>
+
+#include <asm/time.h>
+#include <asm/sgialib.h>
+#include <asm/sn/klconfig.h>
+#include <asm/sn/arch.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/agent.h>
+
+#include "ip27-common.h"
+
+static int rt_next_event(unsigned long delta, struct clock_event_device *evt)
+{
+	unsigned int cpu = smp_processor_id();
+	int slice = cputoslice(cpu);
+	unsigned long cnt;
+
+	cnt = LOCAL_HUB_L(PI_RT_COUNT);
+	cnt += delta;
+	LOCAL_HUB_S(PI_RT_COMPARE_A + PI_COUNT_OFFSET * slice, cnt);
+
+	return LOCAL_HUB_L(PI_RT_COUNT) >= cnt ? -ETIME : 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, hub_rt_clockevent);
+static DEFINE_PER_CPU(char [11], hub_rt_name);
+
+static irqreturn_t hub_rt_counter_handler(int irq, void *dev_id)
+{
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
+	int slice = cputoslice(cpu);
+
+	/*
+	 * Ack
+	 */
+	LOCAL_HUB_S(PI_RT_PEND_A + PI_COUNT_OFFSET * slice, 0);
+	cd->event_handler(cd);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * This is a hack; we really need to figure these values out dynamically
+ *
+ * Since 800 ns works very well with various HUB frequencies, such as
+ * 360, 380, 390 and 400 MHZ, we use 800 ns rtc cycle time.
+ *
+ * Ralf: which clock rate is used to feed the counter?
+ */
+#define NSEC_PER_CYCLE		800
+#define CYCLES_PER_SEC		(NSEC_PER_SEC / NSEC_PER_CYCLE)
+
+void hub_rt_clock_event_init(void)
+{
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
+	unsigned char *name = per_cpu(hub_rt_name, cpu);
+
+	sprintf(name, "hub-rt %d", cpu);
+	cd->name		= name;
+	cd->features		= CLOCK_EVT_FEAT_ONESHOT;
+	clockevent_set_clock(cd, CYCLES_PER_SEC);
+	cd->max_delta_ns	= clockevent_delta2ns(0xfffffffffffff, cd);
+	cd->max_delta_ticks	= 0xfffffffffffff;
+	cd->min_delta_ns	= clockevent_delta2ns(0x300, cd);
+	cd->min_delta_ticks	= 0x300;
+	cd->rating		= 200;
+	cd->irq			= IP27_RT_TIMER_IRQ;
+	cd->cpumask		= cpumask_of(cpu);
+	cd->set_next_event	= rt_next_event;
+	clockevents_register_device(cd);
+
+	enable_percpu_irq(IP27_RT_TIMER_IRQ, IRQ_TYPE_NONE);
+}
+
+static void __init hub_rt_clock_event_global_init(void)
+{
+	irq_set_handler(IP27_RT_TIMER_IRQ, handle_percpu_devid_irq);
+	irq_set_percpu_devid(IP27_RT_TIMER_IRQ);
+	WARN_ON(request_percpu_irq(IP27_RT_TIMER_IRQ, hub_rt_counter_handler,
+				   "hub-rt", &hub_rt_clockevent));
+}
+
+static u64 hub_rt_read(struct clocksource *cs)
+{
+	return REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT);
+}
+
+struct clocksource hub_rt_clocksource = {
+	.name	= "HUB-RT",
+	.rating = 200,
+	.read	= hub_rt_read,
+	.mask	= CLOCKSOURCE_MASK(52),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static u64 notrace hub_rt_read_sched_clock(void)
+{
+	return REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT);
+}
+
+static void __init hub_rt_clocksource_init(void)
+{
+	struct clocksource *cs = &hub_rt_clocksource;
+
+	clocksource_register_hz(cs, CYCLES_PER_SEC);
+
+	sched_clock_register(hub_rt_read_sched_clock, 52, CYCLES_PER_SEC);
+}
+
+void __init plat_time_init(void)
+{
+	hub_rt_clocksource_init();
+	hub_rt_clock_event_global_init();
+	hub_rt_clock_event_init();
+}
+
+void hub_rtc_init(nasid_t nasid)
+{
+
+	/*
+	 * We only need to initialize the current node.
+	 * If this is not the current node then it is a cpuless
+	 * node and timeouts will not happen there.
+	 */
+	if (get_nasid() == nasid) {
+		LOCAL_HUB_S(PI_RT_EN_A, 1);
+		LOCAL_HUB_S(PI_RT_EN_B, 1);
+		LOCAL_HUB_S(PI_PROF_EN_A, 0);
+		LOCAL_HUB_S(PI_PROF_EN_B, 0);
+		LOCAL_HUB_S(PI_RT_COUNT, 0);
+		LOCAL_HUB_S(PI_RT_PEND_A, 0);
+		LOCAL_HUB_S(PI_RT_PEND_B, 0);
+	}
+}