/*
Search @list for element with key @key.
The nodes next, cur and prev are returned in @hp.
Returns true if a node with key @key was found.
This function cannot be called from a signal nor within interrupt context*.
XXX A variant that works within interrupted is possible if needed.
* interrupt context is when the current thread is reposible for another thread
been suspended at an arbritary point. This is a limitation of our SMR implementation.
*/
gboolean
mono_lls_find (MonoLinkedListSet *list, MonoThreadHazardPointers *hp, uintptr_t key)
{
MonoLinkedListSetNode *cur, *next;
MonoLinkedListSetNode **prev;
uintptr_t cur_key;
try_again:
prev = &list->head;
/*
* prev is not really a hazardous pointer, but we return prev
* in hazard pointer 2, so we set it here. Note also that
* prev is not a pointer to a node. We use here the fact that
* the first element in a node is the next pointer, so it
* works, but it's not pretty.
*/
mono_hazard_pointer_set (hp, 2, prev);
cur = get_hazardous_pointer_with_mask ((gpointer*)prev, hp, 1);
while (1) {
if (cur == NULL)
return FALSE;
next = get_hazardous_pointer_with_mask ((gpointer*)&cur->next, hp, 0);
cur_key = cur->key;
/*
* We need to make sure that we dereference prev below
* after reading cur->next above, so we need a read
* barrier.
*/
mono_memory_read_barrier ();
if (*prev != cur)
goto try_again;
if (!mono_lls_pointer_get_mark (next)) {
if (cur_key >= key)
return cur_key == key;
prev = &cur->next;
mono_hazard_pointer_set (hp, 2, cur);
} else {
next = mono_lls_pointer_unmask (next);
if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, next, cur) == cur) {
/* The hazard pointer must be cleared after the CAS. */
mono_memory_write_barrier ();
mono_hazard_pointer_clear (hp, 1);
if (list->free_node_func)
mono_thread_hazardous_free_or_queue (cur, list->free_node_func);
} else
goto try_again;
}
cur = mono_lls_pointer_unmask (next);
mono_hazard_pointer_set (hp, 1, cur);
}
}
gpointer
get_hazardous_pointer_with_mask (gpointer volatile *pp, MonoThreadHazardPointers *hp, int hazard_index)
{
gpointer p;
for (;;) {
/* Get the pointer */
p = *pp;
/* If we don't have hazard pointers just return the
pointer. */
if (!hp)
return p;
/* Make it hazardous */
mono_hazard_pointer_set (hp, hazard_index, mono_lls_pointer_unmask (p));
mono_memory_barrier ();
/* Check that it's still the same. If not, try
again. */
if (*pp != p) {
mono_hazard_pointer_clear (hp, hazard_index);
continue;
}
break;
}
return p;
}
/*
Search @list for element with key @key.
The nodes next, cur and prev are returned in @hp
Returns true if @value was removed by this call.
This function cannot be called from a signal nor with the world stopped.
*/
gboolean
mono_lls_remove (MonoLinkedListSet *list, MonoThreadHazardPointers *hp, MonoLinkedListSetNode *value)
{
MonoLinkedListSetNode *cur, **prev, *next;
while (1) {
if (!mono_lls_find (list, hp, value->key))
return FALSE;
next = mono_hazard_pointer_get_val (hp, 0);
cur = mono_hazard_pointer_get_val (hp, 1);
prev = mono_hazard_pointer_get_val (hp, 2);
g_assert (cur == value);
if (InterlockedCompareExchangePointer ((volatile gpointer*)&cur->next, mask (next, 1), next) != next)
continue;
/* The second CAS must happen before the first. */
mono_memory_write_barrier ();
if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, mono_lls_pointer_unmask (next), cur) == cur) {
/* The CAS must happen before the hazard pointer clear. */
mono_memory_write_barrier ();
mono_hazard_pointer_clear (hp, 1);
if (list->free_node_func)
mono_thread_hazardous_free_or_queue (value, list->free_node_func, FALSE, TRUE);
} else
mono_lls_find (list, hp, value->key);
return TRUE;
}
}
