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/*
* Copyright (c) 2008, 2009, 2010, 2011, 2013, 2014 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef RCULIST_H
#define RCULIST_H 1
/* A single writer multiple RCU-reader doubly linked list.
*
* RCU readers may iterate over the list at the same time as a writer is
* modifying the list. Multiple writers can be supported by use of mutual
* exclusion, but rculist does not provide that, as the user of rculist
* typically does that already.
*
* To be RCU-friendly, the struct rculist instances must be freed via
* ovsrcu_postpone().
*
* The API is almost the same as for struct ovs_list, with the following
* exceptions:
*
* - The 'prev' pointer may not be accessed by the user.
* - The 'next' pointer should be accessed via rculist_next() by readers, and
* rculist_next_protected() by the writer.
* - No rculist_moved(): due to the memory management limitation stated above,
* rculist instances may not be reallocated, as realloc may instantly free
* the old memory.
* - rculist_front() returns a const pointer to accommodate for an RCU reader.
* - rculist_splice_hidden(): Spliced elements may not have been visible to
* RCU readers before the operation.
* - rculist_poison(): Only poisons the 'prev' pointer.
*
* The following functions are variations of the struct ovs_list functions with
* similar names, but are now restricted to the writer use:
*
* - rculist_back_protected()
* - rculist_is_short_protected()
* - rculist_is_singleton_protected()
*/
#include <stdbool.h>
#include <stddef.h>
#include "ovs-rcu.h"
#include "util.h"
/* A non-existing mutex to make it more difficult for an user to accidentally
* keep using the 'prev' pointer. This may be helpful when porting code from
* struct ovs_list to rculist. */
extern struct ovs_mutex rculist_fake_mutex;
/* Doubly linked list head or element. */
struct rculist {
/* Previous list element. */
struct rculist *prev OVS_GUARDED_BY(rculist_fake_mutex);
/* Next list element. */
OVSRCU_TYPE(struct rculist *) next;
};
/* Easier access to 'next' member. */
static inline const struct rculist *rculist_next(const struct rculist *);
static inline struct rculist *rculist_next_protected(const struct rculist *);
/* List initialization. */
#define RCUOVS_LIST_INITIALIZER(LIST) { LIST, OVSRCU_INITIALIZER(LIST) }
static inline void rculist_init(struct rculist *list);
static inline void rculist_poison(struct rculist *elem);
/* List insertion. */
static inline void rculist_insert(struct rculist *list, struct rculist *elem);
static inline void rculist_splice_hidden(struct rculist *before,
struct rculist *first,
struct rculist *last);
static inline void rculist_push_front(struct rculist *list,
struct rculist *elem);
static inline void rculist_push_back(struct rculist *list,
struct rculist *elem);
static inline void rculist_replace(struct rculist *replacement,
struct rculist *replaced);
static inline void rculist_move(struct rculist *dst, struct rculist *src);
/* List removal. */
static inline struct rculist *rculist_remove(struct rculist *elem);
static inline struct rculist *rculist_pop_front(struct rculist *list);
static inline struct rculist *rculist_pop_back(struct rculist *list);
/* List elements. */
static inline const struct rculist *rculist_front(const struct rculist *);
static inline struct rculist *rculist_back_protected(const struct rculist *);
/* List properties. */
static inline size_t rculist_size(const struct rculist *);
static inline bool rculist_is_empty(const struct rculist *);
static inline bool rculist_is_singleton_protected(const struct rculist *);
static inline bool rculist_is_short_protected(const struct rculist *);
/* Inline implementations. */
static inline const struct rculist *
rculist_next(const struct rculist *list)
{
return ovsrcu_get(struct rculist *, &list->next);
}
static inline struct rculist *
rculist_next_protected(const struct rculist *list)
{
return ovsrcu_get_protected(struct rculist *, &list->next);
}
static inline void
rculist_init(struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
list->prev = list;
ovsrcu_init(&list->next, list);
}
#define RCULIST_POISON (struct rculist *)(UINTPTR_MAX / 0xf * 0xc)
/* Initializes 'list' with pointers that will (probably) cause segfaults if
* dereferenced and, better yet, show up clearly in a debugger. */
static inline void
rculist_poison(struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
list->prev = RCULIST_POISON;
}
/* Initializes 'list' with pointers that will (probably) cause segfaults if
* dereferenced and, better yet, show up clearly in a debugger.
*
* This variant poisons also the next pointer, so this may not be called if
* this list element is still visible to RCU readers. */
static inline void
rculist_poison__(struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
rculist_poison(list);
ovsrcu_set_hidden(&list->next, RCULIST_POISON);
}
/* rculist insertion. */
static inline void
rculist_insert(struct rculist *before, struct rculist *elem)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
elem->prev = before->prev;
ovsrcu_set_hidden(&elem->next, before);
ovsrcu_set(&before->prev->next, elem);
before->prev = elem;
}
/* Removes elements 'first' though 'last' (exclusive) from their current list,
* which may NOT be visible to any other threads (== be hidden from them),
* then inserts them just before 'before'. */
static inline void
rculist_splice_hidden(struct rculist *before, struct rculist *first,
struct rculist *last)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct rculist *last_next;
if (first == last) {
return;
}
last = last->prev;
/* Cleanly remove 'first'...'last' from its current list. */
last_next = rculist_next_protected(last);
last_next->prev = first->prev;
ovsrcu_set_hidden(&first->prev->next, last_next);
/* Splice 'first'...'last' into new list. */
first->prev = before->prev;
ovsrcu_set(&last->next, before);
ovsrcu_set(&before->prev->next, first);
before->prev = last;
}
/* Inserts 'elem' at the beginning of 'list', so that it becomes the front in
* 'list'. */
static inline void
rculist_push_front(struct rculist *list, struct rculist *elem)
{
rculist_insert(rculist_next_protected(list), elem);
}
/* Inserts 'elem' at the end of 'list', so that it becomes the back in
* 'list'. */
static inline void
rculist_push_back(struct rculist *list, struct rculist *elem)
{
rculist_insert(list, elem);
}
/* Puts 'element' in the position currently occupied by 'position'.
*
* Afterward, 'position' is not linked to from the list any more, but still
* links to the nodes in the list, and may still be referenced by other threads
* until all other threads quiesce. The replaced node ('position') may not be
* re-inserted, re-initialized, or deleted until after all other threads have
* quiesced (use ovsrcu_postpone). */
static inline void
rculist_replace(struct rculist *element, struct rculist *position)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct rculist *position_next = rculist_next_protected(position);
ovsrcu_set_hidden(&element->next, position_next);
position_next->prev = element;
element->prev = position->prev;
ovsrcu_set(&element->prev->next, element);
rculist_poison(position);
}
/* Initializes 'dst' with the contents of 'src', compensating for moving it
* around in memory. The effect is that, if 'src' was the head of a list, now
* 'dst' is the head of a list containing the same elements.
*
* Memory for 'src' must be kept around until the next RCU quiescent period.
* rculist cannot be simply reallocated, so there is no rculist_moved(). */
static inline void
rculist_move(struct rculist *dst, struct rculist *src)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
if (!rculist_is_empty(src)) {
struct rculist *src_next = rculist_next_protected(src);
dst->prev = src->prev;
ovsrcu_set_hidden(&dst->next, src_next);
src_next->prev = dst;
ovsrcu_set(&src->prev->next, dst);
} else {
rculist_init(dst);
}
rculist_poison(src);
}
/* Removes 'elem' from its list and returns the element that followed it.
* Has no effect when 'elem' is initialized, but not in a list.
* Undefined behavior if 'elem' is not initialized.
*
* Afterward, 'elem' is not linked to from the list any more, but still links
* to the nodes in the list, and may still be referenced by other threads until
* all other threads quiesce. The removed node ('elem') may not be
* re-inserted, re-initialized, or deleted until after all other threads have
* quiesced (use ovsrcu_postpone).
*/
static inline struct rculist *
rculist_remove(struct rculist *elem)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct rculist *elem_next = rculist_next_protected(elem);
elem_next->prev = elem->prev;
ovsrcu_set(&elem->prev->next, elem_next);
rculist_poison(elem);
return elem_next;
}
/* Removes the front element from 'list' and returns it. Undefined behavior if
* 'list' is empty before removal.
*
* Afterward, teh returned former first node is not linked to from the list any
* more, but still links to the nodes in the list, and may still be referenced
* by other threads until all other threads quiesce. The returned node may not
* be re-inserted, re-initialized, or deleted until after all other threads
* have quiesced (use ovsrcu_postpone). */
static inline struct rculist *
rculist_pop_front(struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct rculist *front = rculist_next_protected(list);
rculist_remove(front);
return front;
}
/* Removes the back element from 'list' and returns it.
* Undefined behavior if 'list' is empty before removal.
*
* Afterward, teh returned former last node is not linked to from the list any
* more, but still links to the nodes in the list, and may still be referenced
* by other threads until all other threads quiesce. The returned node may not
* be re-inserted, re-initialized, or deleted until after all other threads
* have quiesced (use ovsrcu_postpone). */
static inline struct rculist *
rculist_pop_back(struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct rculist *back = list->prev;
rculist_remove(back);
return back;
}
/* Returns the front element in 'list_'.
* Undefined behavior if 'list_' is empty. */
static inline const struct rculist *
rculist_front(const struct rculist *list)
{
ovs_assert(!rculist_is_empty(list));
return rculist_next(list);
}
/* Returns the back element in 'list_'.
* Returns the 'list_' itself, if 'list_' is empty. */
static inline struct rculist *
rculist_back_protected(const struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
return CONST_CAST(struct rculist *, list)->prev;
}
/* Returns the number of elements in 'list'.
* Runs in O(n) in the number of elements. */
static inline size_t
rculist_size(const struct rculist *list)
{
const struct rculist *e;
size_t cnt = 0;
for (e = rculist_next(list); e != list; e = rculist_next(e)) {
cnt++;
}
return cnt;
}
/* Returns true if 'list' is empty, false otherwise. */
static inline bool
rculist_is_empty(const struct rculist *list)
{
return rculist_next(list) == list;
}
/* Returns true if 'list' has 0 or 1 elements, false otherwise. */
static inline bool
rculist_is_short_protected(const struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
return rculist_next_protected(list) == list->prev;
}
/* Returns true if 'list' has exactly 1 element, false otherwise. */
static inline bool
rculist_is_singleton_protected(const struct rculist *list)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
const struct rculist *list_next = rculist_next_protected(list);
return list_next == list->prev && list_next != list;
}
#define RCULIST_FOR_EACH(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR(ITER, MEMBER, rculist_next(RCULIST), \
const struct rculist); \
CONDITION_MULTIVAR(ITER, MEMBER, ITER_VAR(ITER) != (RCULIST)); \
UPDATE_MULTIVAR(ITER, rculist_next(ITER_VAR(ITER))))
#define RCULIST_FOR_EACH_CONTINUE(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR(ITER, MEMBER, rculist_next(&(ITER)->MEMBER), \
const struct rculist); \
CONDITION_MULTIVAR(ITER, MEMBER, ITER_VAR(ITER) != (RCULIST)); \
UPDATE_MULTIVAR(ITER, rculist_next(ITER_VAR(ITER))))
#define RCULIST_FOR_EACH_REVERSE_PROTECTED(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR(ITER, MEMBER, rculist_back_protected(RCULIST), \
struct rculist); \
CONDITION_MULTIVAR(ITER, MEMBER, ITER_VAR(ITER) != (RCULIST)); \
UPDATE_MULTIVAR(ITER, rculist_back_protected(ITER_VAR(ITER))))
#define RCULIST_FOR_EACH_REVERSE_PROTECTED_CONTINUE(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR(ITER, MEMBER, rculist_back_protected(ITER->MEMBER), \
struct rculist); \
CONDITION_MULTIVAR(ITER, MEMBER, ITER_VAR(ITER) != (RCULIST)); \
UPDATE_MULTIVAR(ITER, ITER_VAR(ITER)->prev))
#define RCULIST_FOR_EACH_PROTECTED(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR(ITER, MEMBER, rculist_next_protected(RCULIST), \
struct rculist); \
CONDITION_MULTIVAR(ITER, MEMBER, ITER_VAR(ITER) != (RCULIST)); \
UPDATE_MULTIVAR(ITER, rculist_next_protected(ITER_VAR(ITER)))) \
#define RCULIST_FOR_EACH_SAFE_SHORT_PROTECTED(ITER, MEMBER, RCULIST) \
for (INIT_MULTIVAR_SAFE_SHORT(ITER, MEMBER, \
rculist_next_protected(RCULIST), \
struct rculist); \
CONDITION_MULTIVAR_SAFE_SHORT(ITER, MEMBER, \
ITER_VAR(ITER) != (RCULIST), \
ITER_NEXT_VAR(ITER) = rculist_next_protected(ITER_VAR(ITER))); \
UPDATE_MULTIVAR_SAFE_SHORT(ITER))
#define RCULIST_FOR_EACH_SAFE_LONG_PROTECTED(ITER, NEXT, MEMBER, RCULIST) \
for (INIT_MULTIVAR_SAFE_LONG(ITER, NEXT, MEMBER, \
rculist_next_protected(RCULIST), \
struct rculist); \
CONDITION_MULTIVAR_SAFE_LONG(ITER, NEXT, MEMBER, \
ITER_VAR(ITER) != (RCULIST), \
ITER_VAR(NEXT) = rculist_next_protected(ITER_VAR(ITER)), \
ITER_VAR(NEXT) != (RCULIST)); \
UPDATE_MULTIVAR_SAFE_LONG(ITER, NEXT))
#define RCULIST_FOR_EACH_SAFE_PROTECTED(...) \
OVERLOAD_SAFE_MACRO(RCULIST_FOR_EACH_SAFE_LONG_PROTECTED, \
RCULIST_FOR_EACH_SAFE_SHORT_PROTECTED, \
4, __VA_ARGS__)
#endif /* rculist.h */
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