lib: mempool: Synchronize level checks

Do not perform early level usage check. This can lead to situation
where block is seen as available on level when it was taken from
the other context.

Fixes: zephyrproject-rtos#14504

Signed-off-by: Pawel Dunaj <[email protected]>

Author: pdunaj

lib/os/mempool.c

@@ -16,11 +16,6 @@
 #define LVL_ARRAY_SZ(n) (n)
 #endif
 
-static bool level_empty(struct sys_mem_pool_base *p, int l)
-{
-	return sys_dlist_is_empty(&p->levels[l].free_list);
-}
-
 static void *block_ptr(struct sys_mem_pool_base *p, size_t lsz, int block)
 {
 	return (u8_t *)p->buf + lsz * block;
@@ -236,7 +231,7 @@ static void *block_break(struct sys_mem_pool_base *p, void *block, int l,
 int z_sys_mem_pool_block_alloc(struct sys_mem_pool_base *p, size_t size,
 			      u32_t *level_p, u32_t *block_p, void **data_p)
 {
-	int i, from_l, alloc_l = -1, free_l = -1;
+	int i, from_l, alloc_l = -1;
 	unsigned int key;
 	void *data = NULL;
 	size_t lsizes[LVL_ARRAY_SZ(p->n_levels)];
@@ -258,12 +253,9 @@ int z_sys_mem_pool_block_alloc(struct sys_mem_pool_base *p, size_t size,
 		}
 
 		alloc_l = i;
-		if (!level_empty(p, i)) {
-			free_l = i;
-		}
 	}
 
-	if (alloc_l < 0 || free_l < 0) {
+	if (alloc_l < 0) {
 		*data_p = NULL;
 		return -ENOMEM;
 	}
@@ -280,7 +272,7 @@ int z_sys_mem_pool_block_alloc(struct sys_mem_pool_base *p, size_t size,
 	 * spurious -ENOMEM.
 	 */
 	key = pool_irq_lock(p);
-	for (i = free_l; i >= 0; i--) {
+	for (i = alloc_l; i >= 0; i--) {
 		data = block_alloc(p, i, lsizes[i]);
 
 		/* Found one.  Iteratively break it down to the size
@@ -290,9 +282,9 @@ int z_sys_mem_pool_block_alloc(struct sys_mem_pool_base *p, size_t size,
 		 */
 		if (data != NULL) {
 			for (from_l = i; from_l < alloc_l; from_l++) {
-				data = block_break(p, data, from_l, lsizes);
 				pool_irq_unlock(p, key);
 				key = pool_irq_lock(p);
+				data = block_break(p, data, from_l, lsizes);
 			}
 			break;
 		}