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, 226 insertions, 0 deletions

diff --git a/sound/firewire/iso-resources.c b/sound/firewire/iso-resources.c
new file mode 100644
index 000000000..4f6327922
--- /dev/null
+++ b/sound/firewire/iso-resources.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * isochronous resources helper functions
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ */
+
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/firewire-constants.h>
+#include <linux/export.h>
+#include <linux/jiffies.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include "iso-resources.h"
+
+/**
+ * fw_iso_resources_init - initializes a &struct fw_iso_resources
+ * @r: the resource manager to initialize
+ * @unit: the device unit for which the resources will be needed
+ *
+ * If the device does not support all channel numbers, change @r->channels_mask
+ * after calling this function.
+ */
+int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
+{
+	r->channels_mask = ~0uLL;
+	r->unit = unit;
+	mutex_init(&r->mutex);
+	r->allocated = false;
+
+	return 0;
+}
+EXPORT_SYMBOL(fw_iso_resources_init);
+
+/**
+ * fw_iso_resources_destroy - destroy a resource manager
+ * @r: the resource manager that is no longer needed
+ */
+void fw_iso_resources_destroy(struct fw_iso_resources *r)
+{
+	WARN_ON(r->allocated);
+	mutex_destroy(&r->mutex);
+}
+EXPORT_SYMBOL(fw_iso_resources_destroy);
+
+static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed)
+{
+	unsigned int bytes, s400_bytes;
+
+	/* iso packets have three header quadlets and quadlet-aligned payload */
+	bytes = 3 * 4 + ALIGN(max_payload_bytes, 4);
+
+	/* convert to bandwidth units (quadlets at S1600 = bytes at S400) */
+	if (speed <= SCODE_400)
+		s400_bytes = bytes * (1 << (SCODE_400 - speed));
+	else
+		s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400));
+
+	return s400_bytes;
+}
+
+static int current_bandwidth_overhead(struct fw_card *card)
+{
+	/*
+	 * Under the usual pessimistic assumption (cable length 4.5 m), the
+	 * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or
+	 * 88.3 + N * 24.3 in bandwidth units.
+	 *
+	 * The calculation below tries to deduce N from the current gap count.
+	 * If the gap count has been optimized by measuring the actual packet
+	 * transmission time, this derived overhead should be near the actual
+	 * overhead as well.
+	 */
+	return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512;
+}
+
+static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card)
+{
+	for (;;) {
+		s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64();
+		if (delay <= 0)
+			return 0;
+		if (schedule_timeout_interruptible(delay) > 0)
+			return -ERESTARTSYS;
+	}
+}
+
+/**
+ * fw_iso_resources_allocate - allocate isochronous channel and bandwidth
+ * @r: the resource manager
+ * @max_payload_bytes: the amount of data (including CIP headers) per packet
+ * @speed: the speed (e.g., SCODE_400) at which the packets will be sent
+ *
+ * This function allocates one isochronous channel and enough bandwidth for the
+ * specified packet size.
+ *
+ * Returns the channel number that the caller must use for streaming, or
+ * a negative error code.  Due to potentionally long delays, this function is
+ * interruptible and can return -ERESTARTSYS.  On success, the caller is
+ * responsible for calling fw_iso_resources_update() on bus resets, and
+ * fw_iso_resources_free() when the resources are not longer needed.
+ */
+int fw_iso_resources_allocate(struct fw_iso_resources *r,
+			      unsigned int max_payload_bytes, int speed)
+{
+	struct fw_card *card = fw_parent_device(r->unit)->card;
+	int bandwidth, channel, err;
+
+	if (WARN_ON(r->allocated))
+		return -EBADFD;
+
+	r->bandwidth = packet_bandwidth(max_payload_bytes, speed);
+
+retry_after_bus_reset:
+	scoped_guard(spinlock_irq, &card->lock) {
+		r->generation = card->generation;
+		r->bandwidth_overhead = current_bandwidth_overhead(card);
+	}
+
+	err = wait_isoch_resource_delay_after_bus_reset(card);
+	if (err < 0)
+		return err;
+
+	scoped_guard(mutex, &r->mutex) {
+		bandwidth = r->bandwidth + r->bandwidth_overhead;
+		fw_iso_resource_manage(card, r->generation, r->channels_mask,
+				       &channel, &bandwidth, true);
+		if (channel == -EAGAIN)
+			goto retry_after_bus_reset;
+		if (channel >= 0) {
+			r->channel = channel;
+			r->allocated = true;
+		} else {
+			if (channel == -EBUSY)
+				dev_err(&r->unit->device,
+					"isochronous resources exhausted\n");
+			else
+				dev_err(&r->unit->device,
+					"isochronous resource allocation failed\n");
+		}
+	}
+
+	return channel;
+}
+EXPORT_SYMBOL(fw_iso_resources_allocate);
+
+/**
+ * fw_iso_resources_update - update resource allocations after a bus reset
+ * @r: the resource manager
+ *
+ * This function must be called from the driver's .update handler to reallocate
+ * any resources that were allocated before the bus reset.  It is safe to call
+ * this function if no resources are currently allocated.
+ *
+ * Returns a negative error code on failure.  If this happens, the caller must
+ * stop streaming.
+ */
+int fw_iso_resources_update(struct fw_iso_resources *r)
+{
+	struct fw_card *card = fw_parent_device(r->unit)->card;
+	int bandwidth, channel;
+
+	guard(mutex)(&r->mutex);
+
+	if (!r->allocated)
+		return 0;
+
+	scoped_guard(spinlock_irq, &card->lock) {
+		r->generation = card->generation;
+		r->bandwidth_overhead = current_bandwidth_overhead(card);
+	}
+
+	bandwidth = r->bandwidth + r->bandwidth_overhead;
+
+	fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
+			       &channel, &bandwidth, true);
+	/*
+	 * When another bus reset happens, pretend that the allocation
+	 * succeeded; we will try again for the new generation later.
+	 */
+	if (channel < 0 && channel != -EAGAIN) {
+		r->allocated = false;
+		if (channel == -EBUSY)
+			dev_err(&r->unit->device,
+				"isochronous resources exhausted\n");
+		else
+			dev_err(&r->unit->device,
+				"isochronous resource allocation failed\n");
+	}
+
+	return channel;
+}
+EXPORT_SYMBOL(fw_iso_resources_update);
+
+/**
+ * fw_iso_resources_free - frees allocated resources
+ * @r: the resource manager
+ *
+ * This function deallocates the channel and bandwidth, if allocated.
+ */
+void fw_iso_resources_free(struct fw_iso_resources *r)
+{
+	struct fw_card *card;
+	int bandwidth, channel;
+
+	/* Not initialized. */
+	if (r->unit == NULL)
+		return;
+	card = fw_parent_device(r->unit)->card;
+
+	guard(mutex)(&r->mutex);
+
+	if (r->allocated) {
+		bandwidth = r->bandwidth + r->bandwidth_overhead;
+		fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
+				       &channel, &bandwidth, false);
+		if (channel < 0)
+			dev_err(&r->unit->device,
+				"isochronous resource deallocation failed\n");
+
+		r->allocated = false;
+	}
+}
+EXPORT_SYMBOL(fw_iso_resources_free);