2 * mono-split-ordered-list.c: A lock-free split ordered list.
5 * Rodrigo Kumpera (kumpera@gmail.com)
9 * This is an implementation of Maged Michael's lock-free linked-list set.
10 * For more details see:
11 * "High Performance Dynamic Lock-Free Hash Tables and List-Based Sets"
12 * Maged M. Michael 2002
14 * http://www.research.ibm.com/people/m/michael/spaa-2002.pdf
17 #include <mono/utils/mono-linked-list-set.h>
19 #include <mono/utils/atomic.h>
21 static inline gpointer
22 mask (gpointer n, uintptr_t bit)
24 return (gpointer)(((uintptr_t)n) | bit);
28 get_hazardous_pointer_with_mask (gpointer volatile *pp, MonoThreadHazardPointers *hp, int hazard_index)
35 /* If we don't have hazard pointers just return the
39 /* Make it hazardous */
40 mono_hazard_pointer_set (hp, hazard_index, mono_lls_pointer_unmask (p));
42 mono_memory_barrier ();
44 /* Check that it's still the same. If not, try
47 mono_hazard_pointer_clear (hp, hazard_index);
57 Initialize @list and will use @free_node_func to release memory.
58 If @free_node_func is null the caller is responsible for releasing node memory.
59 @free_node_func must be lock-free. That implies that it cannot use malloc/free.
62 mono_lls_init (MonoLinkedListSet *list, void (*free_node_func)(void *))
65 list->free_node_func = free_node_func;
69 Search @list for element with key @key.
70 The nodes next, cur and prev are returned in @hp.
71 Returns true if a node with key @key was found.
72 This function cannot be called from a signal nor within interrupt context*.
73 XXX A variant that works within interrupted is possible if needed.
75 * interrupt context is when the current thread is reposible for another thread
76 been suspended at an arbritary point. This is a limitation of our SMR implementation.
79 mono_lls_find (MonoLinkedListSet *list, MonoThreadHazardPointers *hp, uintptr_t key)
81 MonoLinkedListSetNode *cur, *next;
82 MonoLinkedListSetNode **prev;
89 * prev is not really a hazardous pointer, but we return prev
90 * in hazard pointer 2, so we set it here. Note also that
91 * prev is not a pointer to a node. We use here the fact that
92 * the first element in a node is the next pointer, so it
93 * works, but it's not pretty.
95 mono_hazard_pointer_set (hp, 2, prev);
97 cur = get_hazardous_pointer_with_mask ((gpointer*)prev, hp, 1);
102 next = get_hazardous_pointer_with_mask ((gpointer*)&cur->next, hp, 0);
106 * We need to make sure that we dereference prev below
107 * after reading cur->next above, so we need a read
110 mono_memory_read_barrier ();
115 if (!mono_lls_pointer_get_mark (next)) {
117 return cur_key == key;
120 mono_hazard_pointer_set (hp, 2, cur);
122 next = mono_lls_pointer_unmask (next);
123 if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, next, cur) == cur) {
124 /* The hazard pointer must be cleared after the CAS. */
125 mono_memory_write_barrier ();
126 mono_hazard_pointer_clear (hp, 1);
127 if (list->free_node_func)
128 mono_thread_hazardous_free_or_queue (cur, list->free_node_func, FALSE, TRUE);
132 cur = mono_lls_pointer_unmask (next);
133 mono_hazard_pointer_set (hp, 1, cur);
138 Insert @value into @list.
139 The nodes value, cur and prev are returned in @hp.
140 Return true if @value was inserted by this call. If it returns FALSE, it's the caller
141 resposibility to release memory.
142 This function cannot be called from a signal nor with the world stopped.
145 mono_lls_insert (MonoLinkedListSet *list, MonoThreadHazardPointers *hp, MonoLinkedListSetNode *value)
147 MonoLinkedListSetNode *cur, **prev;
148 /*We must do a store barrier before inserting
149 to make sure all values in @node are globally visible.*/
150 mono_memory_barrier ();
153 if (mono_lls_find (list, hp, value->key))
155 cur = mono_hazard_pointer_get_val (hp, 1);
156 prev = mono_hazard_pointer_get_val (hp, 2);
159 mono_hazard_pointer_set (hp, 0, value);
160 /* The CAS must happen after setting the hazard pointer. */
161 mono_memory_write_barrier ();
162 if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, value, cur) == cur)
168 Search @list for element with key @key.
169 The nodes next, cur and prev are returned in @hp
170 Returns true if @value was removed by this call.
171 This function cannot be called from a signal nor with the world stopped.
174 mono_lls_remove (MonoLinkedListSet *list, MonoThreadHazardPointers *hp, MonoLinkedListSetNode *value)
176 MonoLinkedListSetNode *cur, **prev, *next;
178 if (!mono_lls_find (list, hp, value->key))
181 next = mono_hazard_pointer_get_val (hp, 0);
182 cur = mono_hazard_pointer_get_val (hp, 1);
183 prev = mono_hazard_pointer_get_val (hp, 2);
185 g_assert (cur == value);
187 if (InterlockedCompareExchangePointer ((volatile gpointer*)&cur->next, mask (next, 1), next) != next)
189 /* The second CAS must happen before the first. */
190 mono_memory_write_barrier ();
191 if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, next, cur) == cur) {
192 /* The CAS must happen before the hazard pointer clear. */
193 mono_memory_write_barrier ();
194 mono_hazard_pointer_clear (hp, 1);
195 if (list->free_node_func)
196 mono_thread_hazardous_free_or_queue (value, list->free_node_func, FALSE, TRUE);
198 mono_lls_find (list, hp, value->key);