[PATCH v4 5/5] failsafe: make sub-device remove flag thread-safe

[Luc Pelletier <lucp.at.work@gmail.com>]

For each sub-device, there's a remove flag that's used to indicate if
the sub-device has been removed or not. This flag is currently a
volatile bit field. Even if it's marked as volatile, a bit field is not
thread-safe according to the C standard.

The remove flag is now an unsigned int rather than a bit field. We also
now use the atomic built-ins to read/write the value of the remove flag
to ensure thread-safety.

Fixes: 598fb8aec6f6 ("net/failsafe: support device removal")
Cc: Gaetan Rivet <grive@u256.net>
Cc: stable@dpdk.org

Signed-off-by: Luc Pelletier <lucp.at.work@gmail.com>
---
 drivers/net/failsafe/failsafe_ether.c   | 8 ++++----
 drivers/net/failsafe/failsafe_ops.c     | 2 +-
 drivers/net/failsafe/failsafe_private.h | 4 ++--
 drivers/net/failsafe/failsafe_rxtx.c    | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/failsafe/failsafe_ether.c b/drivers/net/failsafe/failsafe_ether.c
index 3bfc446638..9014777e52 100644
--- a/drivers/net/failsafe/failsafe_ether.c
+++ b/drivers/net/failsafe/failsafe_ether.c
@@ -311,7 +311,7 @@ fs_dev_remove(struct sub_device *sdev)
 		/* the end */
 		break;
 	}
-	sdev->remove = 0;
+	__atomic_store_n(&sdev->remove, 0, __ATOMIC_RELEASE);
 	failsafe_hotplug_alarm_install(fs_dev(sdev));
 }
 
@@ -388,7 +388,7 @@ failsafe_dev_remove(struct rte_eth_dev *dev)
 	uint8_t i;
 
 	FOREACH_SUBDEV(sdev, i, dev) {
-		if (!sdev->remove)
+		if (!__atomic_load_n(&sdev->remove, __ATOMIC_ACQUIRE))
 			continue;
 
 		/* Active devices must have finished their burst and
@@ -556,7 +556,7 @@ failsafe_eth_dev_state_sync(struct rte_eth_dev *dev)
 err_remove:
 	FOREACH_SUBDEV(sdev, i, dev)
 		if (sdev->state != PRIV(dev)->state)
-			sdev->remove = 1;
+			__atomic_store_n(&sdev->remove, 1, __ATOMIC_RELEASE);
 	return ret;
 }
 
@@ -597,7 +597,7 @@ failsafe_eth_rmv_event_callback(uint16_t port_id __rte_unused,
 	 * Async removal, the sub-PMD will try to unregister
 	 * the callback at the source of the current thread context.
 	 */
-	sdev->remove = 1;
+	__atomic_store_n(&sdev->remove, 1, __ATOMIC_RELEASE);
 	fs_unlock(fs_dev(sdev), 0);
 	return 0;
 }
diff --git a/drivers/net/failsafe/failsafe_ops.c b/drivers/net/failsafe/failsafe_ops.c
index b66dfa269b..e65c8a261a 100644
--- a/drivers/net/failsafe/failsafe_ops.c
+++ b/drivers/net/failsafe/failsafe_ops.c
@@ -837,7 +837,7 @@ fs_link_update(struct rte_eth_dev *dev,
 		if (likely(sdev_link_ret == 0)) {
 			if (TX_SUBDEV(dev) == sdev)
 				ret = rte_eth_linkstatus_set(dev, &link_info);
-		} else if (sdev->remove == 0 &&
+		} else if (__atomic_load_n(&sdev->remove, __ATOMIC_ACQUIRE) == 0 &&
 				rte_eth_dev_is_removed(PORT_ID(sdev)) == 0) {
 			ERROR("Link get failed for sub_device %d with error %d",
 				i, sdev_link_ret);
diff --git a/drivers/net/failsafe/failsafe_private.h b/drivers/net/failsafe/failsafe_private.h
index 3865f2fc34..0577a62ab2 100644
--- a/drivers/net/failsafe/failsafe_private.h
+++ b/drivers/net/failsafe/failsafe_private.h
@@ -131,7 +131,7 @@ struct sub_device {
 	/* sub device port id*/
 	uint16_t sdev_port_id; /* shared between processes */
 	/* flag calling for recollection */
-	volatile unsigned int remove:1;
+	unsigned int remove;
 	/* flow isolation state */
 	int flow_isolated:1;
 	/* RMV callback registration state */
@@ -490,7 +490,7 @@ static inline int
 fs_err(struct sub_device *sdev, int err)
 {
 	/* A device removal shouldn't be reported as an error. */
-	if (sdev->remove == 1 || err == -EIO)
+	if (__atomic_load_n(&sdev->remove, __ATOMIC_ACQUIRE) == 1 || err == -EIO)
 		return rte_errno = 0;
 	return err;
 }
diff --git a/drivers/net/failsafe/failsafe_rxtx.c b/drivers/net/failsafe/failsafe_rxtx.c
index 6d8ab0a6e7..c5caab4204 100644
--- a/drivers/net/failsafe/failsafe_rxtx.c
+++ b/drivers/net/failsafe/failsafe_rxtx.c
@@ -16,7 +16,7 @@ fs_rx_unsafe(struct sub_device *sdev)
 	return (ETH(sdev) == NULL) ||
 		(ETH(sdev)->rx_pkt_burst == NULL) ||
 		(sdev->state != DEV_STARTED) ||
-		(sdev->remove != 0);
+		(__atomic_load_n(&sdev->remove, __ATOMIC_ACQUIRE) != 0);
 }
 
 static inline int
-- 
2.38.1