[PATCH 0/2] common/mlx5: fix multi-process mempool registration

[PATCH 0/2] common/mlx5: fix multi-process mempool registration

[Dmitry Kozlyuk]

Dmitry Kozlyuk (2):
  mempool: make event callbacks process-private
  common/mlx5: fix multi-process mempool registration

 drivers/common/mlx5/mlx5_common.c    | 15 ++++----
 drivers/common/mlx5/mlx5_common_mr.c |  2 +-
 drivers/common/mlx5/mlx5_common_mr.h |  2 +-
 lib/mempool/rte_mempool.c            | 54 ++++++++--------------------
 lib/mempool/rte_mempool.h            |  2 ++
 5 files changed, 27 insertions(+), 48 deletions(-)

-- 
2.25.1

[PATCH 1/2] mempool: make event callbacks process-private

[Dmitry Kozlyuk]

Callbacks for mempool events were registered in a process-shared tailq.
This was inherently incorrect because the same function
may be loaded to a different address in each process.
Make the tailq process-private.
Use the EAL tailq lock to reduce the number of different locks
this module operates.

Fixes: da2b9cb25e5f ("mempool: add event callbacks")
Cc: stable@dpdk.org

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
---
 lib/mempool/rte_mempool.c | 54 ++++++++++-----------------------------
 lib/mempool/rte_mempool.h |  2 ++
 2 files changed, 16 insertions(+), 40 deletions(-)

diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
index de59009baf..1e039f6247 100644
--- a/lib/mempool/rte_mempool.c
+++ b/lib/mempool/rte_mempool.c
@@ -36,12 +36,10 @@ static struct rte_tailq_elem rte_mempool_tailq = {
 };
 EAL_REGISTER_TAILQ(rte_mempool_tailq)
 
-TAILQ_HEAD(mempool_callback_list, rte_tailq_entry);
+TAILQ_HEAD(mempool_callback_tailq, mempool_callback_data);
 
-static struct rte_tailq_elem callback_tailq = {
-	.name = "RTE_MEMPOOL_CALLBACK",
-};
-EAL_REGISTER_TAILQ(callback_tailq)
+static struct mempool_callback_tailq callback_tailq =
+		TAILQ_HEAD_INITIALIZER(callback_tailq);
 
 /* Invoke all registered mempool event callbacks. */
 static void
@@ -1372,6 +1370,7 @@ void rte_mempool_walk(void (*func)(struct rte_mempool *, void *),
 }
 
 struct mempool_callback_data {
+	TAILQ_ENTRY(mempool_callback_data) callbacks;
 	rte_mempool_event_callback *func;
 	void *user_data;
 };
@@ -1380,14 +1379,11 @@ static void
 mempool_event_callback_invoke(enum rte_mempool_event event,
 			      struct rte_mempool *mp)
 {
-	struct mempool_callback_list *list;
-	struct rte_tailq_entry *te;
+	struct mempool_callback_data *cb;
 	void *tmp_te;
 
 	rte_mcfg_tailq_read_lock();
-	list = RTE_TAILQ_CAST(callback_tailq.head, mempool_callback_list);
-	RTE_TAILQ_FOREACH_SAFE(te, list, next, tmp_te) {
-		struct mempool_callback_data *cb = te->data;
+	RTE_TAILQ_FOREACH_SAFE(cb, &callback_tailq, callbacks, tmp_te) {
 		rte_mcfg_tailq_read_unlock();
 		cb->func(event, mp, cb->user_data);
 		rte_mcfg_tailq_read_lock();
@@ -1399,10 +1395,7 @@ int
 rte_mempool_event_callback_register(rte_mempool_event_callback *func,
 				    void *user_data)
 {
-	struct mempool_callback_list *list;
-	struct rte_tailq_entry *te = NULL;
 	struct mempool_callback_data *cb;
-	void *tmp_te;
 	int ret;
 
 	if (func == NULL) {
@@ -1411,36 +1404,23 @@ rte_mempool_event_callback_register(rte_mempool_event_callback *func,
 	}
 
 	rte_mcfg_tailq_write_lock();
-	list = RTE_TAILQ_CAST(callback_tailq.head, mempool_callback_list);
-	RTE_TAILQ_FOREACH_SAFE(te, list, next, tmp_te) {
-		cb = te->data;
+	TAILQ_FOREACH(cb, &callback_tailq, callbacks) {
 		if (cb->func == func && cb->user_data == user_data) {
 			ret = -EEXIST;
 			goto exit;
 		}
 	}
 
-	te = rte_zmalloc("mempool_cb_tail_entry", sizeof(*te), 0);
-	if (te == NULL) {
-		RTE_LOG(ERR, MEMPOOL,
-			"Cannot allocate event callback tailq entry!\n");
-		ret = -ENOMEM;
-		goto exit;
-	}
-
-	cb = rte_malloc("mempool_cb_data", sizeof(*cb), 0);
+	cb = calloc(1, sizeof(*cb));
 	if (cb == NULL) {
-		RTE_LOG(ERR, MEMPOOL,
-			"Cannot allocate event callback!\n");
-		rte_free(te);
+		RTE_LOG(ERR, MEMPOOL, "Cannot allocate event callback!\n");
 		ret = -ENOMEM;
 		goto exit;
 	}
 
 	cb->func = func;
 	cb->user_data = user_data;
-	te->data = cb;
-	TAILQ_INSERT_TAIL(list, te, next);
+	TAILQ_INSERT_TAIL(&callback_tailq, cb, callbacks);
 	ret = 0;
 
 exit:
@@ -1453,27 +1433,21 @@ int
 rte_mempool_event_callback_unregister(rte_mempool_event_callback *func,
 				      void *user_data)
 {
-	struct mempool_callback_list *list;
-	struct rte_tailq_entry *te = NULL;
 	struct mempool_callback_data *cb;
 	int ret = -ENOENT;
 
 	rte_mcfg_tailq_write_lock();
-	list = RTE_TAILQ_CAST(callback_tailq.head, mempool_callback_list);
-	TAILQ_FOREACH(te, list, next) {
-		cb = te->data;
+	TAILQ_FOREACH(cb, &callback_tailq, callbacks) {
 		if (cb->func == func && cb->user_data == user_data) {
-			TAILQ_REMOVE(list, te, next);
+			TAILQ_REMOVE(&callback_tailq, cb, callbacks);
 			ret = 0;
 			break;
 		}
 	}
 	rte_mcfg_tailq_write_unlock();
 
-	if (ret == 0) {
-		rte_free(te);
-		rte_free(cb);
-	}
+	if (ret == 0)
+		free(cb);
 	rte_errno = -ret;
 	return ret;
 }
diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
index 3ada37cb86..bfc1f3c823 100644
--- a/lib/mempool/rte_mempool.h
+++ b/lib/mempool/rte_mempool.h
@@ -1847,6 +1847,8 @@ typedef void (rte_mempool_event_callback)(
  * Register a callback function invoked on mempool life cycle event.
  * The function will be invoked in the process
  * that performs an action which triggers the callback.
+ * Registration is process-private,
+ * i.e. each process must manage callbacks on its own if needed.
  *
  * @param func
  *   Callback function.
-- 
2.25.1

[PATCH 2/2] common/mlx5: fix multi-process mempool registration

[Dmitry Kozlyuk]

The `mp_cb_registered` flag shared between all processes
was used to ensure that for any IB device (MLX5 common device)
mempool event callback was registered only once
and mempools that had been existing before the device start
were traversed only once to register them.
Since mempool callback registrations have become process-private,
callback registration must be done by every process.
The flag can no longer reflect the state for any single process.
Replace it with a registration counter to track
when no more callbacks are registered for the device in any process.
It is sufficient to only register pre-existing mempools
in the primary process because it is the one that starts the device.

Fixes: 690b2a88c2f7 ("common/mlx5: add mempool registration facilities")
Cc: stable@dpdk.org

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
---
 drivers/common/mlx5/mlx5_common.c    | 15 +++++++++------
 drivers/common/mlx5/mlx5_common_mr.c |  2 +-
 drivers/common/mlx5/mlx5_common_mr.h |  2 +-
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/common/mlx5/mlx5_common.c b/drivers/common/mlx5/mlx5_common.c
index 89fef2b535..4dcc8cc49c 100644
--- a/drivers/common/mlx5/mlx5_common.c
+++ b/drivers/common/mlx5/mlx5_common.c
@@ -583,18 +583,17 @@ mlx5_dev_mempool_subscribe(struct mlx5_common_device *cdev)
 	if (!cdev->config.mr_mempool_reg_en)
 		return 0;
 	rte_rwlock_write_lock(&cdev->mr_scache.mprwlock);
-	if (cdev->mr_scache.mp_cb_registered)
-		goto exit;
 	/* Callback for this device may be already registered. */
 	ret = rte_mempool_event_callback_register(mlx5_dev_mempool_event_cb,
 						  cdev);
 	if (ret != 0 && rte_errno != EEXIST)
 		goto exit;
+	__atomic_add_fetch(&cdev->mr_scache.mempool_cb_reg_n, 1,
+			   __ATOMIC_ACQUIRE);
 	/* Register mempools only once for this device. */
-	if (ret == 0)
+	if (rte_eal_process_type() == RTE_PROC_PRIMARY)
 		rte_mempool_walk(mlx5_dev_mempool_register_cb, cdev);
 	ret = 0;
-	cdev->mr_scache.mp_cb_registered = 1;
 exit:
 	rte_rwlock_write_unlock(&cdev->mr_scache.mprwlock);
 	return ret;
@@ -603,10 +602,14 @@ mlx5_dev_mempool_subscribe(struct mlx5_common_device *cdev)
 static void
 mlx5_dev_mempool_unsubscribe(struct mlx5_common_device *cdev)
 {
+	uint32_t mempool_cb_reg_n;
 	int ret;
 
-	if (!cdev->mr_scache.mp_cb_registered ||
-	    !cdev->config.mr_mempool_reg_en)
+	if (!cdev->config.mr_mempool_reg_en)
+		return;
+	mempool_cb_reg_n = __atomic_sub_fetch(&cdev->mr_scache.mempool_cb_reg_n,
+					      1, __ATOMIC_RELEASE);
+	if (mempool_cb_reg_n > 0)
 		return;
 	/* Stop watching for mempool events and unregister all mempools. */
 	ret = rte_mempool_event_callback_unregister(mlx5_dev_mempool_event_cb,
diff --git a/drivers/common/mlx5/mlx5_common_mr.c b/drivers/common/mlx5/mlx5_common_mr.c
index 8d8bec99a9..1d54102b54 100644
--- a/drivers/common/mlx5/mlx5_common_mr.c
+++ b/drivers/common/mlx5/mlx5_common_mr.c
@@ -1138,7 +1138,7 @@ mlx5_mr_create_cache(struct mlx5_mr_share_cache *share_cache, int socket)
 			      &share_cache->dereg_mr_cb);
 	rte_rwlock_init(&share_cache->rwlock);
 	rte_rwlock_init(&share_cache->mprwlock);
-	share_cache->mp_cb_registered = 0;
+	share_cache->mempool_cb_reg_n = 0;
 	/* Initialize B-tree and allocate memory for global MR cache table. */
 	return mlx5_mr_btree_init(&share_cache->cache,
 				  MLX5_MR_BTREE_CACHE_N * 2, socket);
diff --git a/drivers/common/mlx5/mlx5_common_mr.h b/drivers/common/mlx5/mlx5_common_mr.h
index 213f5427cb..a5f2d4fd35 100644
--- a/drivers/common/mlx5/mlx5_common_mr.h
+++ b/drivers/common/mlx5/mlx5_common_mr.h
@@ -81,7 +81,7 @@ struct mlx5_mr_share_cache {
 	uint32_t dev_gen; /* Generation number to flush local caches. */
 	rte_rwlock_t rwlock; /* MR cache Lock. */
 	rte_rwlock_t mprwlock; /* Mempool Registration Lock. */
-	uint8_t mp_cb_registered; /* Mempool are Registered. */
+	uint32_t mempool_cb_reg_n; /* Mempool event callabck registrants. */
 	struct mlx5_mr_btree cache; /* Global MR cache table. */
 	struct mlx5_mr_list mr_list; /* Registered MR list. */
 	struct mlx5_mr_list mr_free_list; /* Freed MR list. */
-- 
2.25.1

RE: [PATCH 1/2] mempool: make event callbacks process-private

[Slava Ovsiienko]

> -----Original Message-----
> From: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Sent: Monday, August 8, 2022 12:43
> To: dev@dpdk.org
> Cc: Olivier Matz <olivier.matz@6wind.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; stable@dpdk.org
> Subject: [PATCH 1/2] mempool: make event callbacks process-private
> 
> Callbacks for mempool events were registered in a process-shared tailq.
> This was inherently incorrect because the same function may be loaded to a
> different address in each process.
> Make the tailq process-private.
> Use the EAL tailq lock to reduce the number of different locks this module
> operates.
> 
> Fixes: da2b9cb25e5f ("mempool: add event callbacks")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

RE: [PATCH 2/2] common/mlx5: fix multi-process mempool registration

[Slava Ovsiienko]

> -----Original Message-----
> From: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Sent: Monday, August 8, 2022 12:43
> To: dev@dpdk.org
> Cc: Matan Azrad <matan@nvidia.com>; Slava Ovsiienko
> <viacheslavo@nvidia.com>; stable@dpdk.org
> Subject: [PATCH 2/2] common/mlx5: fix multi-process mempool registration
> 
> The `mp_cb_registered` flag shared between all processes was used to ensure
> that for any IB device (MLX5 common device) mempool event callback was
> registered only once and mempools that had been existing before the device
> start were traversed only once to register them.
> Since mempool callback registrations have become process-private, callback
> registration must be done by every process.
> The flag can no longer reflect the state for any single process.
> Replace it with a registration counter to track when no more callbacks are
> registered for the device in any process.
> It is sufficient to only register pre-existing mempools in the primary
> process because it is the one that starts the device.
> 
> Fixes: 690b2a88c2f7 ("common/mlx5: add mempool registration facilities")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

RE: [PATCH 1/2] mempool: make event callbacks process-private

[Dmitry Kozlyuk]

> From: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Sent: Monday, August 8, 2022 12:43 PM
> To: dev@dpdk.org
> Cc: Olivier Matz <olivier.matz@6wind.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; stable@dpdk.org
> Subject: [PATCH 1/2] mempool: make event callbacks process-private
> 
> Callbacks for mempool events were registered in a process-shared tailq.
> This was inherently incorrect because the same function
> may be loaded to a different address in each process.
> Make the tailq process-private.
> Use the EAL tailq lock to reduce the number of different locks
> this module operates.
> 
> Fixes: da2b9cb25e5f ("mempool: add event callbacks")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>

Kind reminder to the mempool maintainers.

Re: [PATCH 1/2] mempool: make event callbacks process-private

[Andrew Rybchenko]

On 8/28/22 21:33, Slava Ovsiienko wrote:
>> -----Original Message-----
>> From: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
>> Sent: Monday, August 8, 2022 12:43
>> To: dev@dpdk.org
>> Cc: Olivier Matz <olivier.matz@6wind.com>; Andrew Rybchenko
>> <andrew.rybchenko@oktetlabs.ru>; stable@dpdk.org
>> Subject: [PATCH 1/2] mempool: make event callbacks process-private
>>
>> Callbacks for mempool events were registered in a process-shared tailq.
>> This was inherently incorrect because the same function may be loaded to a
>> different address in each process.
>> Make the tailq process-private.
>> Use the EAL tailq lock to reduce the number of different locks this module
>> operates.
>>
>> Fixes: da2b9cb25e5f ("mempool: add event callbacks")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>

Re: [PATCH 0/2] common/mlx5: fix multi-process mempool registration

[Thomas Monjalon]

08/08/2022 11:42, Dmitry Kozlyuk:
> Dmitry Kozlyuk (2):
>   mempool: make event callbacks process-private
>   common/mlx5: fix multi-process mempool registration

Applied, thanks.