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805 lines
29 KiB
805 lines
29 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _LINUX_RCULIST_H |
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#define _LINUX_RCULIST_H |
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|
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#ifdef __KERNEL__ |
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|
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/* |
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* RCU-protected list version |
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*/ |
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#include <linux/list.h> |
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#include <linux/rcupdate.h> |
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|
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/* |
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* INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers |
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* @list: list to be initialized |
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* |
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* You should instead use INIT_LIST_HEAD() for normal initialization and |
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* cleanup tasks, when readers have no access to the list being initialized. |
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* However, if the list being initialized is visible to readers, you |
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* need to keep the compiler from being too mischievous. |
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*/ |
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static inline void INIT_LIST_HEAD_RCU(struct list_head *list) |
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{ |
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WRITE_ONCE(list->next, list); |
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WRITE_ONCE(list->prev, list); |
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} |
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|
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/* |
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* return the ->next pointer of a list_head in an rcu safe |
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* way, we must not access it directly |
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*/ |
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#define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) |
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|
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/** |
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* list_tail_rcu - returns the prev pointer of the head of the list |
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* @head: the head of the list |
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* |
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* Note: This should only be used with the list header, and even then |
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* only if list_del() and similar primitives are not also used on the |
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* list header. |
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*/ |
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#define list_tail_rcu(head) (*((struct list_head __rcu **)(&(head)->prev))) |
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|
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/* |
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* Check during list traversal that we are within an RCU reader |
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*/ |
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#define check_arg_count_one(dummy) |
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|
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#ifdef CONFIG_PROVE_RCU_LIST |
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#define __list_check_rcu(dummy, cond, extra...) \ |
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({ \ |
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check_arg_count_one(extra); \ |
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RCU_LOCKDEP_WARN(!(cond) && !rcu_read_lock_any_held(), \ |
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"RCU-list traversed in non-reader section!"); \ |
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}) |
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#define __list_check_srcu(cond) \ |
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({ \ |
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RCU_LOCKDEP_WARN(!(cond), \ |
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"RCU-list traversed without holding the required lock!");\ |
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}) |
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#else |
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#define __list_check_rcu(dummy, cond, extra...) \ |
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({ check_arg_count_one(extra); }) |
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|
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#define __list_check_srcu(cond) ({ }) |
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#endif |
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/* |
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* Insert a new entry between two known consecutive entries. |
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* |
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* This is only for internal list manipulation where we know |
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* the prev/next entries already! |
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*/ |
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static inline void __list_add_rcu(struct list_head *new, |
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struct list_head *prev, struct list_head *next) |
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{ |
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if (!__list_add_valid(new, prev, next)) |
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return; |
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new->next = next; |
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new->prev = prev; |
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rcu_assign_pointer(list_next_rcu(prev), new); |
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next->prev = new; |
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} |
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/** |
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* list_add_rcu - add a new entry to rcu-protected list |
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* @new: new entry to be added |
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* @head: list head to add it after |
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* |
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* Insert a new entry after the specified head. |
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* This is good for implementing stacks. |
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* |
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* The caller must take whatever precautions are necessary |
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* (such as holding appropriate locks) to avoid racing |
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* with another list-mutation primitive, such as list_add_rcu() |
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* or list_del_rcu(), running on this same list. |
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* However, it is perfectly legal to run concurrently with |
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* the _rcu list-traversal primitives, such as |
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* list_for_each_entry_rcu(). |
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*/ |
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static inline void list_add_rcu(struct list_head *new, struct list_head *head) |
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{ |
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__list_add_rcu(new, head, head->next); |
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} |
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/** |
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* list_add_tail_rcu - add a new entry to rcu-protected list |
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* @new: new entry to be added |
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* @head: list head to add it before |
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* |
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* Insert a new entry before the specified head. |
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* This is useful for implementing queues. |
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* |
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* The caller must take whatever precautions are necessary |
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* (such as holding appropriate locks) to avoid racing |
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* with another list-mutation primitive, such as list_add_tail_rcu() |
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* or list_del_rcu(), running on this same list. |
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* However, it is perfectly legal to run concurrently with |
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* the _rcu list-traversal primitives, such as |
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* list_for_each_entry_rcu(). |
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*/ |
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static inline void list_add_tail_rcu(struct list_head *new, |
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struct list_head *head) |
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{ |
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__list_add_rcu(new, head->prev, head); |
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} |
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|
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/** |
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* list_del_rcu - deletes entry from list without re-initialization |
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* @entry: the element to delete from the list. |
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* |
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* Note: list_empty() on entry does not return true after this, |
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* the entry is in an undefined state. It is useful for RCU based |
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* lockfree traversal. |
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* |
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* In particular, it means that we can not poison the forward |
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* pointers that may still be used for walking the list. |
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* |
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* The caller must take whatever precautions are necessary |
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* (such as holding appropriate locks) to avoid racing |
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* with another list-mutation primitive, such as list_del_rcu() |
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* or list_add_rcu(), running on this same list. |
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* However, it is perfectly legal to run concurrently with |
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* the _rcu list-traversal primitives, such as |
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* list_for_each_entry_rcu(). |
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* |
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* Note that the caller is not permitted to immediately free |
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* the newly deleted entry. Instead, either synchronize_rcu() |
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* or call_rcu() must be used to defer freeing until an RCU |
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* grace period has elapsed. |
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*/ |
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static inline void list_del_rcu(struct list_head *entry) |
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{ |
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__list_del_entry(entry); |
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entry->prev = LIST_POISON2; |
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} |
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/** |
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* hlist_del_init_rcu - deletes entry from hash list with re-initialization |
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* @n: the element to delete from the hash list. |
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* |
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* Note: list_unhashed() on the node return true after this. It is |
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* useful for RCU based read lockfree traversal if the writer side |
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* must know if the list entry is still hashed or already unhashed. |
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* |
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* In particular, it means that we can not poison the forward pointers |
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* that may still be used for walking the hash list and we can only |
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* zero the pprev pointer so list_unhashed() will return true after |
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* this. |
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* |
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* The caller must take whatever precautions are necessary (such as |
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* holding appropriate locks) to avoid racing with another |
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* list-mutation primitive, such as hlist_add_head_rcu() or |
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* hlist_del_rcu(), running on this same list. However, it is |
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* perfectly legal to run concurrently with the _rcu list-traversal |
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* primitives, such as hlist_for_each_entry_rcu(). |
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*/ |
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static inline void hlist_del_init_rcu(struct hlist_node *n) |
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{ |
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if (!hlist_unhashed(n)) { |
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__hlist_del(n); |
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WRITE_ONCE(n->pprev, NULL); |
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} |
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} |
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/** |
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* list_replace_rcu - replace old entry by new one |
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* @old : the element to be replaced |
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* @new : the new element to insert |
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* |
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* The @old entry will be replaced with the @new entry atomically. |
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* Note: @old should not be empty. |
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*/ |
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static inline void list_replace_rcu(struct list_head *old, |
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struct list_head *new) |
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{ |
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new->next = old->next; |
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new->prev = old->prev; |
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rcu_assign_pointer(list_next_rcu(new->prev), new); |
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new->next->prev = new; |
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old->prev = LIST_POISON2; |
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} |
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/** |
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* __list_splice_init_rcu - join an RCU-protected list into an existing list. |
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* @list: the RCU-protected list to splice |
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* @prev: points to the last element of the existing list |
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* @next: points to the first element of the existing list |
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* @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
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* |
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* The list pointed to by @prev and @next can be RCU-read traversed |
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* concurrently with this function. |
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* |
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* Note that this function blocks. |
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* |
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* Important note: the caller must take whatever action is necessary to prevent |
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* any other updates to the existing list. In principle, it is possible to |
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* modify the list as soon as sync() begins execution. If this sort of thing |
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* becomes necessary, an alternative version based on call_rcu() could be |
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* created. But only if -really- needed -- there is no shortage of RCU API |
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* members. |
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*/ |
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static inline void __list_splice_init_rcu(struct list_head *list, |
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struct list_head *prev, |
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struct list_head *next, |
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void (*sync)(void)) |
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{ |
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struct list_head *first = list->next; |
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struct list_head *last = list->prev; |
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/* |
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* "first" and "last" tracking list, so initialize it. RCU readers |
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* have access to this list, so we must use INIT_LIST_HEAD_RCU() |
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* instead of INIT_LIST_HEAD(). |
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*/ |
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INIT_LIST_HEAD_RCU(list); |
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/* |
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* At this point, the list body still points to the source list. |
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* Wait for any readers to finish using the list before splicing |
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* the list body into the new list. Any new readers will see |
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* an empty list. |
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*/ |
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sync(); |
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ASSERT_EXCLUSIVE_ACCESS(*first); |
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ASSERT_EXCLUSIVE_ACCESS(*last); |
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/* |
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* Readers are finished with the source list, so perform splice. |
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* The order is important if the new list is global and accessible |
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* to concurrent RCU readers. Note that RCU readers are not |
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* permitted to traverse the prev pointers without excluding |
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* this function. |
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*/ |
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last->next = next; |
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rcu_assign_pointer(list_next_rcu(prev), first); |
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first->prev = prev; |
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next->prev = last; |
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} |
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/** |
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* list_splice_init_rcu - splice an RCU-protected list into an existing list, |
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* designed for stacks. |
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* @list: the RCU-protected list to splice |
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* @head: the place in the existing list to splice the first list into |
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* @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
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*/ |
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static inline void list_splice_init_rcu(struct list_head *list, |
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struct list_head *head, |
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void (*sync)(void)) |
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{ |
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if (!list_empty(list)) |
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__list_splice_init_rcu(list, head, head->next, sync); |
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} |
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/** |
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* list_splice_tail_init_rcu - splice an RCU-protected list into an existing |
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* list, designed for queues. |
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* @list: the RCU-protected list to splice |
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* @head: the place in the existing list to splice the first list into |
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* @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
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*/ |
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static inline void list_splice_tail_init_rcu(struct list_head *list, |
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struct list_head *head, |
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void (*sync)(void)) |
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{ |
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if (!list_empty(list)) |
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__list_splice_init_rcu(list, head->prev, head, sync); |
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} |
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/** |
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* list_entry_rcu - get the struct for this entry |
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* @ptr: the &struct list_head pointer. |
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* @type: the type of the struct this is embedded in. |
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* @member: the name of the list_head within the struct. |
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* |
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* This primitive may safely run concurrently with the _rcu list-mutation |
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* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
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*/ |
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#define list_entry_rcu(ptr, type, member) \ |
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container_of(READ_ONCE(ptr), type, member) |
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/* |
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* Where are list_empty_rcu() and list_first_entry_rcu()? |
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* |
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* They do not exist because they would lead to subtle race conditions: |
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* |
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* if (!list_empty_rcu(mylist)) { |
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* struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member); |
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* do_something(bar); |
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* } |
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* |
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* The list might be non-empty when list_empty_rcu() checks it, but it |
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* might have become empty by the time that list_first_entry_rcu() rereads |
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* the ->next pointer, which would result in a SEGV. |
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* |
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* When not using RCU, it is OK for list_first_entry() to re-read that |
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* pointer because both functions should be protected by some lock that |
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* blocks writers. |
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* |
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* When using RCU, list_empty() uses READ_ONCE() to fetch the |
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* RCU-protected ->next pointer and then compares it to the address of the |
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* list head. However, it neither dereferences this pointer nor provides |
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* this pointer to its caller. Thus, READ_ONCE() suffices (that is, |
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* rcu_dereference() is not needed), which means that list_empty() can be |
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* used anywhere you would want to use list_empty_rcu(). Just don't |
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* expect anything useful to happen if you do a subsequent lockless |
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* call to list_first_entry_rcu()!!! |
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* |
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* See list_first_or_null_rcu for an alternative. |
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*/ |
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/** |
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* list_first_or_null_rcu - get the first element from a list |
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* @ptr: the list head to take the element from. |
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* @type: the type of the struct this is embedded in. |
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* @member: the name of the list_head within the struct. |
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* |
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* Note that if the list is empty, it returns NULL. |
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* |
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* This primitive may safely run concurrently with the _rcu list-mutation |
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* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
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*/ |
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#define list_first_or_null_rcu(ptr, type, member) \ |
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({ \ |
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struct list_head *__ptr = (ptr); \ |
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struct list_head *__next = READ_ONCE(__ptr->next); \ |
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likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \ |
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}) |
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/** |
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* list_next_or_null_rcu - get the first element from a list |
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* @head: the head for the list. |
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* @ptr: the list head to take the next element from. |
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* @type: the type of the struct this is embedded in. |
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* @member: the name of the list_head within the struct. |
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* |
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* Note that if the ptr is at the end of the list, NULL is returned. |
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* |
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* This primitive may safely run concurrently with the _rcu list-mutation |
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* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
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*/ |
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#define list_next_or_null_rcu(head, ptr, type, member) \ |
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({ \ |
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struct list_head *__head = (head); \ |
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struct list_head *__ptr = (ptr); \ |
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struct list_head *__next = READ_ONCE(__ptr->next); \ |
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likely(__next != __head) ? list_entry_rcu(__next, type, \ |
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member) : NULL; \ |
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}) |
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/** |
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* list_for_each_entry_rcu - iterate over rcu list of given type |
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* @pos: the type * to use as a loop cursor. |
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* @head: the head for your list. |
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* @member: the name of the list_head within the struct. |
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* @cond: optional lockdep expression if called from non-RCU protection. |
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* |
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* This list-traversal primitive may safely run concurrently with |
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* the _rcu list-mutation primitives such as list_add_rcu() |
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* as long as the traversal is guarded by rcu_read_lock(). |
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*/ |
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#define list_for_each_entry_rcu(pos, head, member, cond...) \ |
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for (__list_check_rcu(dummy, ## cond, 0), \ |
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pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
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&pos->member != (head); \ |
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pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
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|
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/** |
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* list_for_each_entry_srcu - iterate over rcu list of given type |
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* @pos: the type * to use as a loop cursor. |
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* @head: the head for your list. |
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* @member: the name of the list_head within the struct. |
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* @cond: lockdep expression for the lock required to traverse the list. |
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* |
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* This list-traversal primitive may safely run concurrently with |
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* the _rcu list-mutation primitives such as list_add_rcu() |
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* as long as the traversal is guarded by srcu_read_lock(). |
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* The lockdep expression srcu_read_lock_held() can be passed as the |
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* cond argument from read side. |
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*/ |
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#define list_for_each_entry_srcu(pos, head, member, cond) \ |
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for (__list_check_srcu(cond), \ |
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pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
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&pos->member != (head); \ |
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pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
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|
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/** |
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* list_entry_lockless - get the struct for this entry |
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* @ptr: the &struct list_head pointer. |
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* @type: the type of the struct this is embedded in. |
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* @member: the name of the list_head within the struct. |
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* |
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* This primitive may safely run concurrently with the _rcu |
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* list-mutation primitives such as list_add_rcu(), but requires some |
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* implicit RCU read-side guarding. One example is running within a special |
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* exception-time environment where preemption is disabled and where lockdep |
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* cannot be invoked. Another example is when items are added to the list, |
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* but never deleted. |
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*/ |
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#define list_entry_lockless(ptr, type, member) \ |
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container_of((typeof(ptr))READ_ONCE(ptr), type, member) |
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|
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/** |
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* list_for_each_entry_lockless - iterate over rcu list of given type |
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* @pos: the type * to use as a loop cursor. |
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* @head: the head for your list. |
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* @member: the name of the list_struct within the struct. |
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* |
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* This primitive may safely run concurrently with the _rcu |
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* list-mutation primitives such as list_add_rcu(), but requires some |
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* implicit RCU read-side guarding. One example is running within a special |
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* exception-time environment where preemption is disabled and where lockdep |
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* cannot be invoked. Another example is when items are added to the list, |
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* but never deleted. |
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*/ |
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#define list_for_each_entry_lockless(pos, head, member) \ |
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for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \ |
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&pos->member != (head); \ |
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pos = list_entry_lockless(pos->member.next, typeof(*pos), member)) |
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|
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/** |
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* list_for_each_entry_continue_rcu - continue iteration over list of given type |
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* @pos: the type * to use as a loop cursor. |
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* @head: the head for your list. |
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* @member: the name of the list_head within the struct. |
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* |
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* Continue to iterate over list of given type, continuing after |
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* the current position which must have been in the list when the RCU read |
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* lock was taken. |
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* This would typically require either that you obtained the node from a |
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* previous walk of the list in the same RCU read-side critical section, or |
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* that you held some sort of non-RCU reference (such as a reference count) |
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* to keep the node alive *and* in the list. |
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* |
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* This iterator is similar to list_for_each_entry_from_rcu() except |
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* this starts after the given position and that one starts at the given |
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* position. |
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*/ |
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#define list_for_each_entry_continue_rcu(pos, head, member) \ |
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for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ |
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&pos->member != (head); \ |
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pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
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|
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/** |
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* list_for_each_entry_from_rcu - iterate over a list from current point |
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* @pos: the type * to use as a loop cursor. |
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* @head: the head for your list. |
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* @member: the name of the list_node within the struct. |
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* |
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* Iterate over the tail of a list starting from a given position, |
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* which must have been in the list when the RCU read lock was taken. |
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* This would typically require either that you obtained the node from a |
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* previous walk of the list in the same RCU read-side critical section, or |
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* that you held some sort of non-RCU reference (such as a reference count) |
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* to keep the node alive *and* in the list. |
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* |
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* This iterator is similar to list_for_each_entry_continue_rcu() except |
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* this starts from the given position and that one starts from the position |
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* after the given position. |
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*/ |
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#define list_for_each_entry_from_rcu(pos, head, member) \ |
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for (; &(pos)->member != (head); \ |
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pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member)) |
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|
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/** |
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* hlist_del_rcu - deletes entry from hash list without re-initialization |
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* @n: the element to delete from the hash list. |
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* |
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* Note: list_unhashed() on entry does not return true after this, |
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* the entry is in an undefined state. It is useful for RCU based |
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* lockfree traversal. |
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* |
|
* In particular, it means that we can not poison the forward |
|
* pointers that may still be used for walking the hash list. |
|
* |
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* The caller must take whatever precautions are necessary |
|
* (such as holding appropriate locks) to avoid racing |
|
* with another list-mutation primitive, such as hlist_add_head_rcu() |
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* or hlist_del_rcu(), running on this same list. |
|
* However, it is perfectly legal to run concurrently with |
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* the _rcu list-traversal primitives, such as |
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* hlist_for_each_entry(). |
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*/ |
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static inline void hlist_del_rcu(struct hlist_node *n) |
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{ |
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__hlist_del(n); |
|
WRITE_ONCE(n->pprev, LIST_POISON2); |
|
} |
|
|
|
/** |
|
* hlist_replace_rcu - replace old entry by new one |
|
* @old : the element to be replaced |
|
* @new : the new element to insert |
|
* |
|
* The @old entry will be replaced with the @new entry atomically. |
|
*/ |
|
static inline void hlist_replace_rcu(struct hlist_node *old, |
|
struct hlist_node *new) |
|
{ |
|
struct hlist_node *next = old->next; |
|
|
|
new->next = next; |
|
WRITE_ONCE(new->pprev, old->pprev); |
|
rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
|
if (next) |
|
WRITE_ONCE(new->next->pprev, &new->next); |
|
WRITE_ONCE(old->pprev, LIST_POISON2); |
|
} |
|
|
|
/** |
|
* hlists_swap_heads_rcu - swap the lists the hlist heads point to |
|
* @left: The hlist head on the left |
|
* @right: The hlist head on the right |
|
* |
|
* The lists start out as [@left ][node1 ... ] and |
|
* [@right ][node2 ... ] |
|
* The lists end up as [@left ][node2 ... ] |
|
* [@right ][node1 ... ] |
|
*/ |
|
static inline void hlists_swap_heads_rcu(struct hlist_head *left, struct hlist_head *right) |
|
{ |
|
struct hlist_node *node1 = left->first; |
|
struct hlist_node *node2 = right->first; |
|
|
|
rcu_assign_pointer(left->first, node2); |
|
rcu_assign_pointer(right->first, node1); |
|
WRITE_ONCE(node2->pprev, &left->first); |
|
WRITE_ONCE(node1->pprev, &right->first); |
|
} |
|
|
|
/* |
|
* return the first or the next element in an RCU protected hlist |
|
*/ |
|
#define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) |
|
#define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) |
|
#define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) |
|
|
|
/** |
|
* hlist_add_head_rcu |
|
* @n: the element to add to the hash list. |
|
* @h: the list to add to. |
|
* |
|
* Description: |
|
* Adds the specified element to the specified hlist, |
|
* while permitting racing traversals. |
|
* |
|
* The caller must take whatever precautions are necessary |
|
* (such as holding appropriate locks) to avoid racing |
|
* with another list-mutation primitive, such as hlist_add_head_rcu() |
|
* or hlist_del_rcu(), running on this same list. |
|
* However, it is perfectly legal to run concurrently with |
|
* the _rcu list-traversal primitives, such as |
|
* hlist_for_each_entry_rcu(), used to prevent memory-consistency |
|
* problems on Alpha CPUs. Regardless of the type of CPU, the |
|
* list-traversal primitive must be guarded by rcu_read_lock(). |
|
*/ |
|
static inline void hlist_add_head_rcu(struct hlist_node *n, |
|
struct hlist_head *h) |
|
{ |
|
struct hlist_node *first = h->first; |
|
|
|
n->next = first; |
|
WRITE_ONCE(n->pprev, &h->first); |
|
rcu_assign_pointer(hlist_first_rcu(h), n); |
|
if (first) |
|
WRITE_ONCE(first->pprev, &n->next); |
|
} |
|
|
|
/** |
|
* hlist_add_tail_rcu |
|
* @n: the element to add to the hash list. |
|
* @h: the list to add to. |
|
* |
|
* Description: |
|
* Adds the specified element to the specified hlist, |
|
* while permitting racing traversals. |
|
* |
|
* The caller must take whatever precautions are necessary |
|
* (such as holding appropriate locks) to avoid racing |
|
* with another list-mutation primitive, such as hlist_add_head_rcu() |
|
* or hlist_del_rcu(), running on this same list. |
|
* However, it is perfectly legal to run concurrently with |
|
* the _rcu list-traversal primitives, such as |
|
* hlist_for_each_entry_rcu(), used to prevent memory-consistency |
|
* problems on Alpha CPUs. Regardless of the type of CPU, the |
|
* list-traversal primitive must be guarded by rcu_read_lock(). |
|
*/ |
|
static inline void hlist_add_tail_rcu(struct hlist_node *n, |
|
struct hlist_head *h) |
|
{ |
|
struct hlist_node *i, *last = NULL; |
|
|
|
/* Note: write side code, so rcu accessors are not needed. */ |
|
for (i = h->first; i; i = i->next) |
|
last = i; |
|
|
|
if (last) { |
|
n->next = last->next; |
|
WRITE_ONCE(n->pprev, &last->next); |
|
rcu_assign_pointer(hlist_next_rcu(last), n); |
|
} else { |
|
hlist_add_head_rcu(n, h); |
|
} |
|
} |
|
|
|
/** |
|
* hlist_add_before_rcu |
|
* @n: the new element to add to the hash list. |
|
* @next: the existing element to add the new element before. |
|
* |
|
* Description: |
|
* Adds the specified element to the specified hlist |
|
* before the specified node while permitting racing traversals. |
|
* |
|
* The caller must take whatever precautions are necessary |
|
* (such as holding appropriate locks) to avoid racing |
|
* with another list-mutation primitive, such as hlist_add_head_rcu() |
|
* or hlist_del_rcu(), running on this same list. |
|
* However, it is perfectly legal to run concurrently with |
|
* the _rcu list-traversal primitives, such as |
|
* hlist_for_each_entry_rcu(), used to prevent memory-consistency |
|
* problems on Alpha CPUs. |
|
*/ |
|
static inline void hlist_add_before_rcu(struct hlist_node *n, |
|
struct hlist_node *next) |
|
{ |
|
WRITE_ONCE(n->pprev, next->pprev); |
|
n->next = next; |
|
rcu_assign_pointer(hlist_pprev_rcu(n), n); |
|
WRITE_ONCE(next->pprev, &n->next); |
|
} |
|
|
|
/** |
|
* hlist_add_behind_rcu |
|
* @n: the new element to add to the hash list. |
|
* @prev: the existing element to add the new element after. |
|
* |
|
* Description: |
|
* Adds the specified element to the specified hlist |
|
* after the specified node while permitting racing traversals. |
|
* |
|
* The caller must take whatever precautions are necessary |
|
* (such as holding appropriate locks) to avoid racing |
|
* with another list-mutation primitive, such as hlist_add_head_rcu() |
|
* or hlist_del_rcu(), running on this same list. |
|
* However, it is perfectly legal to run concurrently with |
|
* the _rcu list-traversal primitives, such as |
|
* hlist_for_each_entry_rcu(), used to prevent memory-consistency |
|
* problems on Alpha CPUs. |
|
*/ |
|
static inline void hlist_add_behind_rcu(struct hlist_node *n, |
|
struct hlist_node *prev) |
|
{ |
|
n->next = prev->next; |
|
WRITE_ONCE(n->pprev, &prev->next); |
|
rcu_assign_pointer(hlist_next_rcu(prev), n); |
|
if (n->next) |
|
WRITE_ONCE(n->next->pprev, &n->next); |
|
} |
|
|
|
#define __hlist_for_each_rcu(pos, head) \ |
|
for (pos = rcu_dereference(hlist_first_rcu(head)); \ |
|
pos; \ |
|
pos = rcu_dereference(hlist_next_rcu(pos))) |
|
|
|
/** |
|
* hlist_for_each_entry_rcu - iterate over rcu list of given type |
|
* @pos: the type * to use as a loop cursor. |
|
* @head: the head for your list. |
|
* @member: the name of the hlist_node within the struct. |
|
* @cond: optional lockdep expression if called from non-RCU protection. |
|
* |
|
* This list-traversal primitive may safely run concurrently with |
|
* the _rcu list-mutation primitives such as hlist_add_head_rcu() |
|
* as long as the traversal is guarded by rcu_read_lock(). |
|
*/ |
|
#define hlist_for_each_entry_rcu(pos, head, member, cond...) \ |
|
for (__list_check_rcu(dummy, ## cond, 0), \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\ |
|
typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_srcu - iterate over rcu list of given type |
|
* @pos: the type * to use as a loop cursor. |
|
* @head: the head for your list. |
|
* @member: the name of the hlist_node within the struct. |
|
* @cond: lockdep expression for the lock required to traverse the list. |
|
* |
|
* This list-traversal primitive may safely run concurrently with |
|
* the _rcu list-mutation primitives such as hlist_add_head_rcu() |
|
* as long as the traversal is guarded by srcu_read_lock(). |
|
* The lockdep expression srcu_read_lock_held() can be passed as the |
|
* cond argument from read side. |
|
*/ |
|
#define hlist_for_each_entry_srcu(pos, head, member, cond) \ |
|
for (__list_check_srcu(cond), \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\ |
|
typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing) |
|
* @pos: the type * to use as a loop cursor. |
|
* @head: the head for your list. |
|
* @member: the name of the hlist_node within the struct. |
|
* |
|
* This list-traversal primitive may safely run concurrently with |
|
* the _rcu list-mutation primitives such as hlist_add_head_rcu() |
|
* as long as the traversal is guarded by rcu_read_lock(). |
|
* |
|
* This is the same as hlist_for_each_entry_rcu() except that it does |
|
* not do any RCU debugging or tracing. |
|
*/ |
|
#define hlist_for_each_entry_rcu_notrace(pos, head, member) \ |
|
for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\ |
|
typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_rcu_bh - iterate over rcu list of given type |
|
* @pos: the type * to use as a loop cursor. |
|
* @head: the head for your list. |
|
* @member: the name of the hlist_node within the struct. |
|
* |
|
* This list-traversal primitive may safely run concurrently with |
|
* the _rcu list-mutation primitives such as hlist_add_head_rcu() |
|
* as long as the traversal is guarded by rcu_read_lock(). |
|
*/ |
|
#define hlist_for_each_entry_rcu_bh(pos, head, member) \ |
|
for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\ |
|
typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point |
|
* @pos: the type * to use as a loop cursor. |
|
* @member: the name of the hlist_node within the struct. |
|
*/ |
|
#define hlist_for_each_entry_continue_rcu(pos, member) \ |
|
for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
|
&(pos)->member)), typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point |
|
* @pos: the type * to use as a loop cursor. |
|
* @member: the name of the hlist_node within the struct. |
|
*/ |
|
#define hlist_for_each_entry_continue_rcu_bh(pos, member) \ |
|
for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
|
&(pos)->member)), typeof(*(pos)), member); \ |
|
pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
/** |
|
* hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point |
|
* @pos: the type * to use as a loop cursor. |
|
* @member: the name of the hlist_node within the struct. |
|
*/ |
|
#define hlist_for_each_entry_from_rcu(pos, member) \ |
|
for (; pos; \ |
|
pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
|
&(pos)->member)), typeof(*(pos)), member)) |
|
|
|
#endif /* __KERNEL__ */ |
|
#endif
|
|
|