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, 191 insertions, 0 deletions

diff --git a/block/blk-pm.c b/block/blk-pm.c
new file mode 100644
index 000000000..8d3e052f9
--- /dev/null
+++ b/block/blk-pm.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/blk-pm.h>
+#include <linux/blkdev.h>
+#include <linux/pm_runtime.h>
+#include "blk-mq.h"
+
+/**
+ * blk_pm_runtime_init - Block layer runtime PM initialization routine
+ * @q: the queue of the device
+ * @dev: the device the queue belongs to
+ *
+ * Description:
+ *    Initialize runtime-PM-related fields for @q and start auto suspend for
+ *    @dev. Drivers that want to take advantage of request-based runtime PM
+ *    should call this function after @dev has been initialized, and its
+ *    request queue @q has been allocated, and runtime PM for it can not happen
+ *    yet(either due to disabled/forbidden or its usage_count > 0). In most
+ *    cases, driver should call this function before any I/O has taken place.
+ *
+ *    This function takes care of setting up using auto suspend for the device,
+ *    the autosuspend delay is set to -1 to make runtime suspend impossible
+ *    until an updated value is either set by user or by driver. Drivers do
+ *    not need to touch other autosuspend settings.
+ *
+ *    The block layer runtime PM is request based, so only works for drivers
+ *    that use request as their IO unit instead of those directly use bio's.
+ */
+void blk_pm_runtime_init(struct request_queue *q, struct device *dev)
+{
+	q->dev = dev;
+	q->rpm_status = RPM_ACTIVE;
+	pm_runtime_set_autosuspend_delay(q->dev, -1);
+	pm_runtime_use_autosuspend(q->dev);
+}
+EXPORT_SYMBOL(blk_pm_runtime_init);
+
+/**
+ * blk_pre_runtime_suspend - Pre runtime suspend check
+ * @q: the queue of the device
+ *
+ * Description:
+ *    This function will check if runtime suspend is allowed for the device
+ *    by examining if there are any requests pending in the queue. If there
+ *    are requests pending, the device can not be runtime suspended; otherwise,
+ *    the queue's status will be updated to SUSPENDING and the driver can
+ *    proceed to suspend the device.
+ *
+ *    For the not allowed case, we mark last busy for the device so that
+ *    runtime PM core will try to autosuspend it some time later.
+ *
+ *    This function should be called near the start of the device's
+ *    runtime_suspend callback.
+ *
+ * Return:
+ *    0		- OK to runtime suspend the device
+ *    -EBUSY	- Device should not be runtime suspended
+ */
+int blk_pre_runtime_suspend(struct request_queue *q)
+{
+	int ret = 0;
+
+	if (!q->dev)
+		return ret;
+
+	WARN_ON_ONCE(q->rpm_status != RPM_ACTIVE);
+
+	spin_lock_irq(&q->queue_lock);
+	q->rpm_status = RPM_SUSPENDING;
+	spin_unlock_irq(&q->queue_lock);
+
+	/*
+	 * Increase the pm_only counter before checking whether any
+	 * non-PM blk_queue_enter() calls are in progress to avoid that any
+	 * new non-PM blk_queue_enter() calls succeed before the pm_only
+	 * counter is decreased again.
+	 */
+	blk_set_pm_only(q);
+	ret = -EBUSY;
+	/* Switch q_usage_counter from per-cpu to atomic mode. */
+	blk_freeze_queue_start(q);
+	/*
+	 * Wait until atomic mode has been reached. Since that
+	 * involves calling call_rcu(), it is guaranteed that later
+	 * blk_queue_enter() calls see the pm-only state. See also
+	 * http://lwn.net/Articles/573497/.
+	 */
+	percpu_ref_switch_to_atomic_sync(&q->q_usage_counter);
+	if (percpu_ref_is_zero(&q->q_usage_counter))
+		ret = 0;
+	/* Switch q_usage_counter back to per-cpu mode. */
+	blk_mq_unfreeze_queue_nomemrestore(q);
+
+	if (ret < 0) {
+		spin_lock_irq(&q->queue_lock);
+		q->rpm_status = RPM_ACTIVE;
+		pm_runtime_mark_last_busy(q->dev);
+		spin_unlock_irq(&q->queue_lock);
+
+		blk_clear_pm_only(q);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(blk_pre_runtime_suspend);
+
+/**
+ * blk_post_runtime_suspend - Post runtime suspend processing
+ * @q: the queue of the device
+ * @err: return value of the device's runtime_suspend function
+ *
+ * Description:
+ *    Update the queue's runtime status according to the return value of the
+ *    device's runtime suspend function and mark last busy for the device so
+ *    that PM core will try to auto suspend the device at a later time.
+ *
+ *    This function should be called near the end of the device's
+ *    runtime_suspend callback.
+ */
+void blk_post_runtime_suspend(struct request_queue *q, int err)
+{
+	if (!q->dev)
+		return;
+
+	spin_lock_irq(&q->queue_lock);
+	if (!err) {
+		q->rpm_status = RPM_SUSPENDED;
+	} else {
+		q->rpm_status = RPM_ACTIVE;
+		pm_runtime_mark_last_busy(q->dev);
+	}
+	spin_unlock_irq(&q->queue_lock);
+
+	if (err)
+		blk_clear_pm_only(q);
+}
+EXPORT_SYMBOL(blk_post_runtime_suspend);
+
+/**
+ * blk_pre_runtime_resume - Pre runtime resume processing
+ * @q: the queue of the device
+ *
+ * Description:
+ *    Update the queue's runtime status to RESUMING in preparation for the
+ *    runtime resume of the device.
+ *
+ *    This function should be called near the start of the device's
+ *    runtime_resume callback.
+ */
+void blk_pre_runtime_resume(struct request_queue *q)
+{
+	if (!q->dev)
+		return;
+
+	spin_lock_irq(&q->queue_lock);
+	q->rpm_status = RPM_RESUMING;
+	spin_unlock_irq(&q->queue_lock);
+}
+EXPORT_SYMBOL(blk_pre_runtime_resume);
+
+/**
+ * blk_post_runtime_resume - Post runtime resume processing
+ * @q: the queue of the device
+ *
+ * Description:
+ *    Restart the queue of a runtime suspended device. It does this regardless
+ *    of whether the device's runtime-resume succeeded; even if it failed the
+ *    driver or error handler will need to communicate with the device.
+ *
+ *    This function should be called near the end of the device's
+ *    runtime_resume callback to correct queue runtime PM status and re-enable
+ *    peeking requests from the queue.
+ */
+void blk_post_runtime_resume(struct request_queue *q)
+{
+	int old_status;
+
+	if (!q->dev)
+		return;
+
+	spin_lock_irq(&q->queue_lock);
+	old_status = q->rpm_status;
+	q->rpm_status = RPM_ACTIVE;
+	pm_runtime_mark_last_busy(q->dev);
+	pm_request_autosuspend(q->dev);
+	spin_unlock_irq(&q->queue_lock);
+
+	if (old_status != RPM_ACTIVE)
+		blk_clear_pm_only(q);
+}
+EXPORT_SYMBOL(blk_post_runtime_resume);