Following are the failure steps:
1. The physical device is removed due to change in one of PF parameters
(e.g. MTU) 2. The interrupt thread flags the device 3. Within 2 seconds
Interrupt thread initializes the actual device removal, then every 2
seconds it tries to re-sync (plug in) the device. The trials fail as
long as VF parameter mismatches the PF parameter.
4. A control thread initiates a control operation on failsafe which
initiates this operation on the device.
5. A race condition occurs between the control thread and interrupt
thread when accessing the device data structures.

This patch mitigates the race condition in step 5.

Fixes: a46f8d584eb8 ("net/failsafe: add fail-safe PMD")
Cc: sta...@dpdk.org

Signed-off-by: Matan Azrad <ma...@mellanox.com>
---
 drivers/net/failsafe/failsafe.c         |  2 +-
 drivers/net/failsafe/failsafe_eal.c     |  2 +-
 drivers/net/failsafe/failsafe_ether.c   |  2 +-
 drivers/net/failsafe/failsafe_ops.c     | 26 +++++++++++++++++--------
 drivers/net/failsafe/failsafe_private.h | 34 ++++++++++++++++++++++++++-------
 5 files changed, 48 insertions(+), 18 deletions(-)

diff --git a/drivers/net/failsafe/failsafe.c b/drivers/net/failsafe/failsafe.c
index 7b2cdbb..6cdefd0 100644
--- a/drivers/net/failsafe/failsafe.c
+++ b/drivers/net/failsafe/failsafe.c
@@ -187,7 +187,7 @@
                 * If MAC address was provided as a parameter,
                 * apply to all probed slaves.
                 */
-               FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_PROBED) {
+               FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_PROBED) {
                        ret = rte_eth_dev_default_mac_addr_set(PORT_ID(sdev),
                                                               mac);
                        if (ret) {
diff --git a/drivers/net/failsafe/failsafe_eal.c 
b/drivers/net/failsafe/failsafe_eal.c
index c3d6731..b3b9c32 100644
--- a/drivers/net/failsafe/failsafe_eal.c
+++ b/drivers/net/failsafe/failsafe_eal.c
@@ -126,7 +126,7 @@
        int sdev_ret;
        int ret = 0;
 
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_PROBED) {
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_PROBED) {
                sdev_ret = rte_eal_hotplug_remove(sdev->bus->name,
                                                        sdev->dev->name);
                if (sdev_ret) {
diff --git a/drivers/net/failsafe/failsafe_ether.c 
b/drivers/net/failsafe/failsafe_ether.c
index ca42376..f2a52c9 100644
--- a/drivers/net/failsafe/failsafe_ether.c
+++ b/drivers/net/failsafe/failsafe_ether.c
@@ -325,7 +325,7 @@
        struct sub_device *sdev;
        uint8_t i;
 
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE)
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE)
                if (sdev->remove && fs_rxtx_clean(sdev)) {
                        fs_dev_stats_save(sdev);
                        fs_dev_remove(sdev);
diff --git a/drivers/net/failsafe/failsafe_ops.c 
b/drivers/net/failsafe/failsafe_ops.c
index a7c2dba..3d2cb32 100644
--- a/drivers/net/failsafe/failsafe_ops.c
+++ b/drivers/net/failsafe/failsafe_ops.c
@@ -181,6 +181,9 @@
        FOREACH_SUBDEV(sdev, i, dev) {
                if (sdev->state != DEV_ACTIVE)
                        continue;
+               if (sdev->remove == 1 && PRIV(dev)->state < DEV_STARTED)
+                       /* Application shouldn't start removed sub-devices. */
+                       continue;
                DEBUG("Starting sub_device %d", i);
                ret = rte_eth_dev_start(PORT_ID(sdev));
                if (ret) {
@@ -265,10 +268,17 @@
        uint8_t i;
 
        failsafe_hotplug_alarm_cancel(dev);
-       if (PRIV(dev)->state == DEV_STARTED)
+       if (PRIV(dev)->state == DEV_STARTED) {
+               /*
+                * Clean remove flags to allow stop for all sub-devices because
+                * there is not hot-plug alarm to stop the removed sub-devices.
+                */
+               FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_STARTED)
+                       sdev->remove = 0;
                dev->dev_ops->dev_stop(dev);
+       }
        PRIV(dev)->state = DEV_ACTIVE - 1;
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE) {
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE) {
                DEBUG("Closing sub_device %d", i);
                rte_eth_dev_close(PORT_ID(sdev));
                sdev->state = DEV_ACTIVE - 1;
@@ -309,7 +319,7 @@
        if (rxq->event_fd > 0)
                close(rxq->event_fd);
        dev = rxq->priv->dev;
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE)
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE)
                SUBOPS(sdev, rx_queue_release)
                        (ETH(sdev)->data->rx_queues[rxq->qid]);
        dev->data->rx_queues[rxq->qid] = NULL;
@@ -376,7 +386,7 @@
                return ret;
        rxq->event_fd = intr_handle.efds[0];
        dev->data->rx_queues[rx_queue_id] = rxq;
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE) {
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE) {
                ret = rte_eth_rx_queue_setup(PORT_ID(sdev),
                                rx_queue_id,
                                nb_rx_desc, socket_id,
@@ -493,7 +503,7 @@
                return;
        txq = queue;
        dev = txq->priv->dev;
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE)
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE)
                SUBOPS(sdev, tx_queue_release)
                        (ETH(sdev)->data->tx_queues[txq->qid]);
        dev->data->tx_queues[txq->qid] = NULL;
@@ -548,7 +558,7 @@
        txq->info.nb_desc = nb_tx_desc;
        txq->priv = PRIV(dev);
        dev->data->tx_queues[tx_queue_id] = txq;
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE) {
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE) {
                ret = rte_eth_tx_queue_setup(PORT_ID(sdev),
                                tx_queue_id,
                                nb_tx_desc, socket_id,
@@ -663,7 +673,7 @@
        int ret;
 
        rte_memcpy(stats, &PRIV(dev)->stats_accumulator, sizeof(*stats));
-       FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_ACTIVE) {
+       FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_ACTIVE) {
                struct rte_eth_stats *snapshot = &sdev->stats_snapshot.stats;
                uint64_t *timestamp = &sdev->stats_snapshot.timestamp;
 
@@ -746,7 +756,7 @@
 
                rx_offload_capa = default_infos.rx_offload_capa;
                rxq_offload_capa = default_infos.rx_queue_offload_capa;
-               FOREACH_SUBDEV_STATE(sdev, i, dev, DEV_PROBED) {
+               FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, DEV_PROBED) {
                        rte_eth_dev_info_get(PORT_ID(sdev),
                                        &PRIV(dev)->infos);
                        rx_offload_capa &= PRIV(dev)->infos.rx_offload_capa;
diff --git a/drivers/net/failsafe/failsafe_private.h 
b/drivers/net/failsafe/failsafe_private.h
index f3be152..7ddd63a 100644
--- a/drivers/net/failsafe/failsafe_private.h
+++ b/drivers/net/failsafe/failsafe_private.h
@@ -244,16 +244,31 @@ int failsafe_eth_lsc_event_callback(uint16_t port_id,
        ((sdev)->sid)
 
 /**
- * Stateful iterator construct over fail-safe sub-devices:
+ * Stateful iterator construct over fail-safe sub-devices,
+ * including the removed sub-devices:
+ * s:     (struct sub_device *), iterator
+ * i:     (uint8_t), increment
+ * dev:   (struct rte_eth_dev *), fail-safe ethdev
+ * state: (enum dev_state), minimum acceptable device state
+ */
+
+#define FOREACH_SUBDEV_STATE_UNSAFE(s, i, dev, state)  \
+       for (s = fs_find_next((dev), 0, state, 0, &i);  \
+            s != NULL;                                 \
+            s = fs_find_next((dev), i + 1, state, 0, &i))
+
+/**
+ * Stateful iterator construct over fail-safe sub-devices,
+ * except the removed sub-devices:
  * s:     (struct sub_device *), iterator
  * i:     (uint8_t), increment
  * dev:   (struct rte_eth_dev *), fail-safe ethdev
  * state: (enum dev_state), minimum acceptable device state
  */
 #define FOREACH_SUBDEV_STATE(s, i, dev, state)         \
-       for (s = fs_find_next((dev), 0, state, &i);     \
+       for (s = fs_find_next((dev), 0, state, 1, &i);  \
             s != NULL;                                 \
-            s = fs_find_next((dev), i + 1, state, &i))
+            s = fs_find_next((dev), i + 1, state, 1, &i))
 
 /**
  * Iterator construct over fail-safe sub-devices:
@@ -262,7 +277,7 @@ int failsafe_eth_lsc_event_callback(uint16_t port_id,
  * dev: (struct rte_eth_dev *), fail-safe ethdev
  */
 #define FOREACH_SUBDEV(s, i, dev)                      \
-       FOREACH_SUBDEV_STATE(s, i, dev, DEV_UNDEFINED)
+       FOREACH_SUBDEV_STATE_UNSAFE(s, i, dev, DEV_UNDEFINED)
 
 /* dev: (struct rte_eth_dev *) fail-safe device */
 #define PREFERRED_SUBDEV(dev) \
@@ -328,6 +343,7 @@ int failsafe_eth_lsc_event_callback(uint16_t port_id,
 fs_find_next(struct rte_eth_dev *dev,
             uint8_t sid,
             enum dev_state min_state,
+            uint8_t check_remove,
             uint8_t *sid_out)
 {
        struct sub_device *subs;
@@ -336,8 +352,12 @@ int failsafe_eth_lsc_event_callback(uint16_t port_id,
        subs = PRIV(dev)->subs;
        tail = PRIV(dev)->subs_tail;
        while (sid < tail) {
-               if (subs[sid].state >= min_state)
-                       break;
+               if (subs[sid].state >= min_state) {
+                       if (check_remove == 0)
+                               break;
+                       if (PRIV(dev)->subs[sid].remove == 0)
+                               break;
+               }
                sid++;
        }
        *sid_out = sid;
@@ -376,7 +396,7 @@ int failsafe_eth_lsc_event_callback(uint16_t port_id,
                uint8_t i;
 
                /* Using acceptable device */
-               FOREACH_SUBDEV_STATE(sdev, i, dev, req_state) {
+               FOREACH_SUBDEV_STATE_UNSAFE(sdev, i, dev, req_state) {
                        if (sdev == banned)
                                continue;
                        DEBUG("Switching tx_dev to sub_device %d",
-- 
1.8.3.1

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