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CLEANUP: pools: do not use the extra pointer to link shared elements

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This practice relying on POOL_LINK() dates from the era where there were
no pool caches, but given that the structures are a bit more complex now
and that pool caches do not make use of this feature, it is totally
useless since released elements have already been overwritten, and yet
it complicates the architecture and prevents from making simplifications
and optimizations. Let's just get rid of this feature. The pointer to
the origin pool is preserved though, as it helps detect incorrect frees
and serves as a canary for overflows.
This commit is contained in:
Willy Tarreau 2021-12-31 16:00:19 +01:00
parent 4859984a5b
commit 799f6143ca
3 changed files with 4 additions and 5 deletions
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1
include/haproxy/pool-t.h
View File

@ -40,7 +40,6 @@
#define POOL_LINK(pool, item) (void **)(((char *)(item)) + ((pool)->size))
#else
#define POOL_EXTRA (0)
#define POOL_LINK(pool, item) ((void **)(item))
#endif
/* A special pointer for the pool's free_list that indicates someone is

4
include/haproxy/pool.h
View File

@ -132,7 +132,7 @@ static inline void *pool_get_from_shared_cache(struct pool_head *pool)
}
/* this releases the lock */
_HA_ATOMIC_STORE(&pool->free_list, *POOL_LINK(pool, ret));
_HA_ATOMIC_STORE(&pool->free_list, *(void **)ret);
_HA_ATOMIC_INC(&pool->used);
#ifdef DEBUG_MEMORY_POOLS
@ -164,7 +164,7 @@ static inline void pool_put_to_shared_cache(struct pool_head *pool, void *ptr)
__ha_cpu_relax();
free_list = _HA_ATOMIC_LOAD(&pool->free_list);
}
_HA_ATOMIC_STORE(POOL_LINK(pool, ptr), (void *)free_list);
_HA_ATOMIC_STORE((void **)ptr, (void *)free_list);
__ha_barrier_atomic_store();
} while (!_HA_ATOMIC_CAS(&pool->free_list, &free_list, ptr));
__ha_barrier_atomic_store();

4
src/pool.c
View File

@ -417,7 +417,7 @@ void pool_flush(struct pool_head *pool)
while (next) {
temp = next;
next = *POOL_LINK(pool, temp);
next = *(void **)temp;
pool_put_to_os(pool, temp);
}
/* here, we should have pool->allocated == pool->used */
@ -442,7 +442,7 @@ void pool_gc(struct pool_head *pool_ctx)
while (entry->free_list &&
(int)(entry->allocated - entry->used) > (int)entry->minavail) {
temp = entry->free_list;
entry->free_list = *POOL_LINK(entry, temp);
entry->free_list = *(void **)temp;
pool_put_to_os(entry, temp);
}
}