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Use Explicit Atomics In The Internal Spinlock #206

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merged 4 commits into from
Mar 26, 2024
Merged

Use Explicit Atomics In The Internal Spinlock #206

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42b7602
Use explicit atomic loads and stores in the internal spinlock impleme…
insertinterestingnamehere Dec 5, 2023
e2c1122
Fix a race condition in the fastlock initialization idiom by restruct…
insertinterestingnamehere Dec 13, 2023
a05ad28
Try re-adding old spinlock body macro to spinlock loop.
insertinterestingnamehere Dec 13, 2023
201efde
Fix intermittent race condition in barrier test resulting from non-at…
insertinterestingnamehere Feb 14, 2024
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22 changes: 11 additions & 11 deletions include/qt_addrstat.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,19 +7,19 @@
* keeping track of the FEB status of an address. It expects a shepherd pointer
* to use to find the right memory pool to use. */
static QINLINE qthread_addrstat_t *qthread_addrstat_new(void)
{ /*{{{ */
{ /*{{{ */
qthread_addrstat_t *ret = ALLOC_ADDRSTAT();
QTHREAD_FASTLOCK_INIT_PTR(&ret->lock);
QTHREAD_FASTLOCK_LOCK(&ret->lock);
ret->full = 1;
ret->valid = 1;
ret->EFQ = NULL;
ret->FEQ = NULL;
ret->FFQ = NULL;
ret->FFWQ = NULL;
QTHREAD_EMPTY_TIMER_INIT(ret);
QTHREAD_FASTLOCK_UNLOCK(&ret->lock);

if (ret != NULL) {
QTHREAD_FASTLOCK_INIT(ret->lock);
ret->full = 1;
ret->valid = 1;
ret->EFQ = NULL;
ret->FEQ = NULL;
ret->FFQ = NULL;
ret->FFWQ = NULL;
QTHREAD_EMPTY_TIMER_INIT(ret);
}
return ret;
} /*}}} */

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18 changes: 7 additions & 11 deletions include/qt_atomics.h
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Expand Up @@ -68,20 +68,16 @@
# define QTHREAD_FASTLOCK_SETUP() do { } while (0)
# define QTHREAD_FASTLOCK_ATTRVAR
typedef struct qt_spin_exclusive_s { /* added to allow fast critical section ordering */
aligned_t enter; /* and not call pthreads spin_lock -- hard to debug */
aligned_t exit; /* near the lock under gdb -- 4/1/11 akp */
aligned_t _Atomic enter; /* and not call pthreads spin_lock -- hard to debug */
aligned_t _Atomic exit; /* near the lock under gdb -- 4/1/11 akp */
} qt_spin_exclusive_t;
void qt_spin_exclusive_lock(qt_spin_exclusive_t *);
void qt_spin_exclusive_unlock(qt_spin_exclusive_t *);
# define QTHREAD_FASTLOCK_INIT(x) { (x).enter = 0; (x).exit = 0; }
# define QTHREAD_FASTLOCK_INIT_PTR(x) { (x)->enter = 0; (x)->exit = 0; }
# define QTHREAD_FASTLOCK_LOCK(x) { aligned_t val = qthread_incr(&(x)->enter, 1); \
while (val != (x)->exit) SPINLOCK_BODY(); \
THREAD_FENCE_MEM_ACQUIRE; /* spin waiting for my turn */ }
# define QTHREAD_FASTLOCK_UNLOCK(x) do { COMPILER_FENCE; \
THREAD_FENCE_MEM_RELEASE; \
(x)->exit++; /* allow next guy's turn */ \
} while (0)
# define QTHREAD_FASTLOCK_INIT(x) { atomic_store_explicit(&(x).enter, 0u, memory_order_release); atomic_store_explicit(&(x).exit, 0u, memory_order_release); }
# define QTHREAD_FASTLOCK_INIT_PTR(x) { atomic_store_explicit(&(x)->enter, 0u, memory_order_release); atomic_store_explicit(&(x)->exit, 0u, memory_order_release); }
# define QTHREAD_FASTLOCK_LOCK(x) { aligned_t val = atomic_fetch_add_explicit(&(x)->enter, 1u, memory_order_relaxed); \
while (val != atomic_load_explicit(&(x)->exit, memory_order_acquire)) SPINLOCK_BODY(); /* spin waiting for turn */ }
# define QTHREAD_FASTLOCK_UNLOCK(x) do { atomic_fetch_add_explicit(&(x)->exit, 1u, memory_order_release); /* notify next waiting thread */} while (0)
# define QTHREAD_FASTLOCK_DESTROY(x)
# define QTHREAD_FASTLOCK_DESTROY_PTR(x)
# define QTHREAD_FASTLOCK_TYPE qt_spin_exclusive_t
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5 changes: 4 additions & 1 deletion src/hashmap.c
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Expand Up @@ -147,10 +147,13 @@ qt_hash INTERNAL qt_hash_create(int needSync)
if (needSync) {
ret->lock = MALLOC(sizeof(QTHREAD_FASTLOCK_TYPE));
QTHREAD_FASTLOCK_INIT_PTR(ret->lock);
QTHREAD_FASTLOCK_LOCK(ret->lock);
qt_hash_internal_create(ret, 100);
QTHREAD_FASTLOCK_UNLOCK(ret->lock);
} else {
ret->lock = NULL;
qt_hash_internal_create(ret, 100);
}
qt_hash_internal_create(ret, 100);
}
return ret;
} /*}}}*/
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26 changes: 15 additions & 11 deletions src/mpool.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ struct qt_mpool_s {
qt_mpool_threadlocal_cache_t *_Atomic caches; // for cleanup

QTHREAD_FASTLOCK_TYPE reuse_lock;
void *reuse_pool;
void *_Atomic reuse_pool;

QTHREAD_FASTLOCK_TYPE pool_lock;
void **alloc_list;
Expand Down Expand Up @@ -200,11 +200,14 @@ qt_mpool INTERNAL qt_mpool_create_aligned(size_t item_size,
alloc_size *= 2;
}
}
pool->alloc_size = alloc_size;
pool->items_per_alloc = alloc_size / item_size;
pool->reuse_pool = NULL;
QTHREAD_FASTLOCK_INIT(pool->reuse_lock);
QTHREAD_FASTLOCK_INIT(pool->pool_lock);
QTHREAD_FASTLOCK_LOCK(&pool->reuse_lock);
atomic_store_explicit(&pool->reuse_pool, NULL, memory_order_relaxed);
QTHREAD_FASTLOCK_UNLOCK(&pool->reuse_lock);
QTHREAD_FASTLOCK_LOCK(&pool->pool_lock);
pool->alloc_size = alloc_size;
pool->items_per_alloc = alloc_size / item_size;
#ifdef TLS
pool->offset = qthread_incr(&pool_cache_global_max, 1);
#else
Expand All @@ -218,6 +221,7 @@ qt_mpool INTERNAL qt_mpool_create_aligned(size_t item_size,
atomic_store_explicit(&pool->alloc_list_pos, 0u, memory_order_relaxed);

atomic_store_explicit(&pool->caches, NULL, memory_order_relaxed);
QTHREAD_FASTLOCK_UNLOCK(&pool->pool_lock);
return pool;

qgoto(errexit);
Expand Down Expand Up @@ -344,14 +348,14 @@ void INTERNAL *qt_mpool_alloc(qt_mpool pool)

cnt = 0;
/* cache is empty; need to fill it */
if (pool->reuse_pool) { // global cache
if (atomic_load_explicit(&pool->reuse_pool, memory_order_relaxed)) { // global cache
qthread_debug(MPOOL_BEHAVIOR, "->...pull from reuse\n");
QTHREAD_FASTLOCK_LOCK(&pool->reuse_lock);
if (pool->reuse_pool) {
cache = pool->reuse_pool;
pool->reuse_pool = atomic_load_explicit(&cache->block_tail->next, memory_order_relaxed);
if (atomic_load_explicit(&pool->reuse_pool, memory_order_relaxed)) {
cache = atomic_load_explicit(&pool->reuse_pool, memory_order_relaxed);
atomic_store_explicit(&pool->reuse_pool, atomic_load_explicit(&cache->block_tail->next, memory_order_relaxed), memory_order_relaxed);
atomic_store_explicit(&cache->block_tail->next, NULL, memory_order_relaxed);
cnt = items_per_alloc;
cnt = items_per_alloc;
}
QTHREAD_FASTLOCK_UNLOCK(&pool->reuse_lock);
}
Expand Down Expand Up @@ -433,8 +437,8 @@ void INTERNAL qt_mpool_free(qt_mpool pool,
assert(toglobal);
assert(atomic_load_explicit(&toglobal->block_tail, memory_order_relaxed));
QTHREAD_FASTLOCK_LOCK(&pool->reuse_lock);
atomic_store_explicit(&atomic_load_explicit(&toglobal->block_tail, memory_order_relaxed)->next, pool->reuse_pool, memory_order_relaxed);
pool->reuse_pool = toglobal;
atomic_store_explicit(&atomic_load_explicit(&toglobal->block_tail, memory_order_relaxed)->next, atomic_load_explicit(&pool->reuse_pool, memory_order_relaxed), memory_order_relaxed);
atomic_store_explicit(&pool->reuse_pool, toglobal, memory_order_relaxed);
QTHREAD_FASTLOCK_UNLOCK(&pool->reuse_lock);
cnt -= items_per_alloc;
} else if (cnt == items_per_alloc + 1) {
Expand Down
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