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BUG/MEDIUM: memory_pool: Update the seq number in pool_flush().

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In pool_flush(), we can't just set the free_list to NULL, or we may suffer
the ABA problem. Instead, use a double-width CAS and update the sequence
number.

This should be backported to 2.1, 2.0 and 1.9.
This may, or may not, be related to github issue #476.
This commit is contained in:
Olivier Houchard 2020-02-01 17:37:22 +01:00
parent 952c2640b0
commit b6fa08bc7b
1 changed files with 7 additions and 2 deletions
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9
src/memory.c
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@ -217,15 +217,20 @@ void *pool_refill_alloc(struct pool_head *pool, unsigned int avail)
*/
void pool_flush(struct pool_head *pool)
{
struct pool_free_list cmp, new;
void **next, *temp;
int removed = 0;
if (!pool)
return;
do {
next = pool->free_list;
} while (!_HA_ATOMIC_CAS(&pool->free_list, &next, NULL));
cmp.free_list = pool->free_list;
cmp.seq = pool->seq;
new.free_list = NULL;
new.seq = cmp.seq + 1;
} while (!_HA_ATOMIC_DWCAS(&pool->free_list, &cmp, &new));
__ha_barrier_atomic_store();
next = cmp.free_list;
while (next) {
temp = next;
next = *POOL_LINK(pool, temp);