From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/md/dm-vdo/wait-queue.h | 138 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 138 insertions(+) create mode 100644 drivers/md/dm-vdo/wait-queue.h (limited to 'drivers/md/dm-vdo/wait-queue.h') diff --git a/drivers/md/dm-vdo/wait-queue.h b/drivers/md/dm-vdo/wait-queue.h new file mode 100644 index 000000000..7e8ee6afe --- /dev/null +++ b/drivers/md/dm-vdo/wait-queue.h @@ -0,0 +1,138 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright 2023 Red Hat + */ + +#ifndef VDO_WAIT_QUEUE_H +#define VDO_WAIT_QUEUE_H + +#include +#include + +/** + * A vdo_wait_queue is a circular singly linked list of entries waiting to be notified + * of a change in a condition. Keeping a circular list allows the vdo_wait_queue + * structure to simply be a pointer to the tail (newest) entry, supporting + * constant-time enqueue and dequeue operations. A null pointer is an empty waitq. + * + * An empty waitq: + * waitq0.last_waiter -> NULL + * + * A singleton waitq: + * waitq1.last_waiter -> entry1 -> entry1 -> [...] + * + * A three-element waitq: + * waitq2.last_waiter -> entry3 -> entry1 -> entry2 -> entry3 -> [...] + * + * linux/wait.h's wait_queue_head is _not_ used because vdo_wait_queue's + * interface is much less complex (doesn't need locking, priorities or timers). + * Made possible by vdo's thread-based resource allocation and locking; and + * the polling nature of vdo_wait_queue consumers. + * + * FIXME: could be made to use a linux/list.h's list_head but its extra barriers + * really aren't needed. Nor is a doubly linked list, but vdo_wait_queue could + * make use of __list_del_clearprev() -- but that would compromise the ability + * to make full use of linux's list interface. + */ + +struct vdo_waiter; + +struct vdo_wait_queue { + /* The tail of the queue, the last (most recently added) entry */ + struct vdo_waiter *last_waiter; + /* The number of waiters currently in the queue */ + size_t length; +}; + +/** + * vdo_waiter_callback_fn - Callback type that will be called to resume processing + * of a waiter after it has been removed from its wait queue. + */ +typedef void (*vdo_waiter_callback_fn)(struct vdo_waiter *waiter, void *context); + +/** + * vdo_waiter_match_fn - Method type for waiter matching methods. + * + * Returns false if the waiter does not match. + */ +typedef bool (*vdo_waiter_match_fn)(struct vdo_waiter *waiter, void *context); + +/* The structure for entries in a vdo_wait_queue. */ +struct vdo_waiter { + /* + * The next waiter in the waitq. If this entry is the last waiter, then this + * is actually a pointer back to the head of the waitq. + */ + struct vdo_waiter *next_waiter; + + /* Optional waiter-specific callback to invoke when dequeuing this waiter. */ + vdo_waiter_callback_fn callback; +}; + +/** + * vdo_waiter_is_waiting() - Check whether a waiter is waiting. + * @waiter: The waiter to check. + * + * Return: true if the waiter is on some vdo_wait_queue. + */ +static inline bool vdo_waiter_is_waiting(struct vdo_waiter *waiter) +{ + return (waiter->next_waiter != NULL); +} + +/** + * vdo_waitq_init() - Initialize a vdo_wait_queue. + * @waitq: The vdo_wait_queue to initialize. + */ +static inline void vdo_waitq_init(struct vdo_wait_queue *waitq) +{ + *waitq = (struct vdo_wait_queue) { + .last_waiter = NULL, + .length = 0, + }; +} + +/** + * vdo_waitq_has_waiters() - Check whether a vdo_wait_queue has any entries waiting. + * @waitq: The vdo_wait_queue to query. + * + * Return: true if there are any waiters in the waitq. + */ +static inline bool __must_check vdo_waitq_has_waiters(const struct vdo_wait_queue *waitq) +{ + return (waitq->last_waiter != NULL); +} + +void vdo_waitq_enqueue_waiter(struct vdo_wait_queue *waitq, + struct vdo_waiter *waiter); + +struct vdo_waiter *vdo_waitq_dequeue_waiter(struct vdo_wait_queue *waitq); + +void vdo_waitq_notify_all_waiters(struct vdo_wait_queue *waitq, + vdo_waiter_callback_fn callback, void *context); + +bool vdo_waitq_notify_next_waiter(struct vdo_wait_queue *waitq, + vdo_waiter_callback_fn callback, void *context); + +void vdo_waitq_transfer_all_waiters(struct vdo_wait_queue *from_waitq, + struct vdo_wait_queue *to_waitq); + +struct vdo_waiter *vdo_waitq_get_first_waiter(const struct vdo_wait_queue *waitq); + +void vdo_waitq_dequeue_matching_waiters(struct vdo_wait_queue *waitq, + vdo_waiter_match_fn waiter_match, + void *match_context, + struct vdo_wait_queue *matched_waitq); + +/** + * vdo_waitq_num_waiters() - Return the number of waiters in a vdo_wait_queue. + * @waitq: The vdo_wait_queue to query. + * + * Return: The number of waiters in the waitq. + */ +static inline size_t __must_check vdo_waitq_num_waiters(const struct vdo_wait_queue *waitq) +{ + return waitq->length; +} + +#endif /* VDO_WAIT_QUEUE_H */ -- cgit v1.3.1