static void*
par_alloc_from_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag, size_t size)
{
char *p = frag->fragment_next;
char *end = p + size;
if (end > frag->fragment_end)
return NULL;
/* p = frag->fragment_next must happen before */
mono_memory_barrier ();
if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->fragment_next, end, p) != p)
return NULL;
if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
SgenFragment *next, **prev_ptr;
/*
* Before we clean the remaining nursery, we must claim the remaining space
* as it could end up been used by the range allocator since it can end up
* allocating from this dying fragment as it doesn't respect SGEN_MAX_NURSERY_WASTE
* when doing second chance allocation.
*/
if ((sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION || sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG) && claim_remaining_size (frag, end)) {
sgen_clear_range (end, frag->fragment_end);
HEAVY_STAT (stat_wasted_bytes_trailer += frag->fragment_end - end);
#ifdef NALLOC_DEBUG
add_alloc_record (end, frag->fragment_end - end, BLOCK_ZEROING);
#endif
}
prev_ptr = find_previous_pointer_fragment (allocator, frag);
/*Use Michaels linked list remove*/
/*prev_ptr will be null if the fragment was removed concurrently */
while (prev_ptr) {
next = frag->next;
/*already deleted*/
if (!get_mark (next)) {
/*frag->next read must happen before the first CAS*/
mono_memory_write_barrier ();
/*Fail if the next node is removed concurrently and its CAS wins */
if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->next, mask (next, 1), next) != next) {
continue;
}
}
/* The second CAS must happen after the first CAS or frag->next. */
mono_memory_write_barrier ();
/* Fail if the previous node was deleted and its CAS wins */
if (InterlockedCompareExchangePointer ((volatile gpointer*)prev_ptr, unmask (next), frag) != frag) {
prev_ptr = find_previous_pointer_fragment (allocator, frag);
continue;
}
break;
}
}
return p;
}
static void*
alloc_from_fragment (Fragment *frag, size_t size)
{
char *p = frag->fragment_next;
char *end = p + size;
if (end > frag->fragment_end)
return NULL;
/* p = frag->fragment_next must happen before */
mono_memory_barrier ();
if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->fragment_next, end, p) != p)
return NULL;
if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
Fragment *next, **prev_ptr;
/*
* Before we clean the remaining nursery, we must claim the remaining space
* as it could end up been used by the range allocator since it can end up
* allocating from this dying fragment as it doesn't respect SGEN_MAX_NURSERY_WASTE
* when doing second chance allocation.
*/
if (mono_sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION && claim_remaining_size (frag, end)) {
/* Clear the remaining space, pinning depends on this. FIXME move this to use phony arrays */
memset (end, 0, frag->fragment_end - end);
HEAVY_STAT (InterlockedExchangeAdd (&stat_wasted_bytes_trailer, frag->fragment_end - end));
#ifdef NALLOC_DEBUG
add_alloc_record (end, frag->fragment_end - end, BLOCK_ZEROING);
#endif
}
prev_ptr = find_previous_pointer_fragment (frag);
/*Use Michaels linked list remove*/
/*prev_ptr will be null is the fragment was removed concurrently */
while (prev_ptr) {
next = frag->next;
/*already deleted*/
if (!get_mark (next)) {
/*frag->next read must happen before the first CAS*/
mono_memory_write_barrier ();
/*Fail if the next done is removed concurrently and its CAS wins */
if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->next, mask (next, 1), next) != next) {
continue;
}
}
/* The second CAS must happen after the first CAS or frag->next. */
mono_memory_write_barrier ();
/* Fail if the previous node was deleted and its CAS wins */
if (InterlockedCompareExchangePointer ((volatile gpointer*)prev_ptr, next, frag) != frag) {
prev_ptr = find_previous_pointer_fragment (frag);
continue;
}
/* No need to membar here since the worst that can happen is a CAS failure. */
do {
frag->next_free = fragment_freelist;
} while (InterlockedCompareExchangePointer ((volatile gpointer*)&fragment_freelist, frag, frag->next_free) != frag->next_free);
break;
}
}
return p;
}