net/mlx5: Delay events till ib registration ends

When mlx5_ib registers itself to mlx5_core as an interface, it will
call mlx5_add_device which will call mlx5_ib interface add callback,
in case the latter successfully returns, only then mlx5_core will add
it to the interface list and async events will be forwarded to mlx5_ib.
Between mlx5_ib interface add callback and mlx5_core adding the mlx5_ib
interface to its devices list, arriving mlx5_core events can be missed
by the new mlx5_ib registering interface.

In other words:
thread 1: mlx5_ib: mlx5_register_interface(dev)
thread 1: mlx5_core: mlx5_add_device(dev)
thread 1: mlx5_core: ctx = dev->add => (mlx5_ib)->mlx5_ib_add
thread 2: mlx5_core_event: **new event arrives, forward to dev_list
thread 1: mlx5_core: add_ctx_to_dev_list(ctx)
/* previous event was missed by the new interface.*/
It is ok to miss events before dev->add (mlx5_ib)->mlx5_ib_add_device
but not after.

We fix this race by accumulating the events that come between the
ib_register_device (inside mlx5_add_device->(dev->add)) till the adding
to the list completes and fire them to the new registering interface
after that.

Fixes: f1ee87fe55c8 ("net/mlx5: Organize device list API in one place")
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

3 files changed, 79 insertions, 0 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/dev.c b/drivers/net/ethernet/mellanox/mlx5/core/dev.c
index a62f4b6a21a5..ff60cf7342ca 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/dev.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/dev.c
@@ -45,11 +45,70 @@ struct mlx5_device_context {
         unsigned long           state;
 };
 
+struct mlx5_delayed_event {
+        struct list_head        list;
+        struct mlx5_core_dev    *dev;
+        enum mlx5_dev_event     event;
+        unsigned long           param;
+};
+
 enum {
         MLX5_INTERFACE_ADDED,
         MLX5_INTERFACE_ATTACHED,
 };
 
+static void add_delayed_event(struct mlx5_priv *priv,
+                              struct mlx5_core_dev *dev,
+                              enum mlx5_dev_event event,
+                              unsigned long param)
+{
+        struct mlx5_delayed_event *delayed_event;
+
+        delayed_event = kzalloc(sizeof(*delayed_event), GFP_ATOMIC);
+        if (!delayed_event) {
+                mlx5_core_err(dev, "event %d is missed\n", event);
+                return;
+        }
+
+        mlx5_core_dbg(dev, "Accumulating event %d\n", event);
+        delayed_event->dev = dev;
+        delayed_event->event = event;
+        delayed_event->param = param;
+        list_add_tail(&delayed_event->list, &priv->waiting_events_list);
+}
+
+static void fire_delayed_event_locked(struct mlx5_device_context *dev_ctx,
+                                      struct mlx5_core_dev *dev,
+                                      struct mlx5_priv *priv)
+{
+        struct mlx5_delayed_event *de;
+        struct mlx5_delayed_event *n;
+
+        /* stop delaying events */
+        priv->is_accum_events = false;
+
+        /* fire all accumulated events before new event comes */
+        list_for_each_entry_safe(de, n, &priv->waiting_events_list, list) {
+                dev_ctx->intf->event(dev, dev_ctx->context, de->event, de->param);
+                list_del(&de->list);
+                kfree(de);
+        }
+}
+
+static void cleanup_delayed_evets(struct mlx5_priv *priv)
+{
+        struct mlx5_delayed_event *de;
+        struct mlx5_delayed_event *n;
+
+        spin_lock_irq(&priv->ctx_lock);
+        priv->is_accum_events = false;
+        list_for_each_entry_safe(de, n, &priv->waiting_events_list, list) {
+                list_del(&de->list);
+                kfree(de);
+        }
+        spin_unlock_irq(&priv->ctx_lock);
+}
+
 void mlx5_add_device(struct mlx5_interface *intf, struct mlx5_priv *priv)
 {
         struct mlx5_device_context *dev_ctx;
@@ -63,6 +122,12 @@ void mlx5_add_device(struct mlx5_interface *intf, struct mlx5_priv *priv)
                 return;
 
         dev_ctx->intf = intf;
+        /* accumulating events that can come after mlx5_ib calls to
+         * ib_register_device, till adding that interface to the events list.
+         */
+
+        priv->is_accum_events = true;
+
         dev_ctx->context = intf->add(dev);
         set_bit(MLX5_INTERFACE_ADDED, &dev_ctx->state);
         if (intf->attach)
@@ -71,6 +136,9 @@ void mlx5_add_device(struct mlx5_interface *intf, struct mlx5_priv *priv)
         if (dev_ctx->context) {
                 spin_lock_irq(&priv->ctx_lock);
                 list_add_tail(&dev_ctx->list, &priv->ctx_list);
+
+                fire_delayed_event_locked(dev_ctx, dev, priv);
+
 #ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
                 if (dev_ctx->intf->pfault) {
                         if (priv->pfault) {
@@ -84,6 +152,8 @@ void mlx5_add_device(struct mlx5_interface *intf, struct mlx5_priv *priv)
                 spin_unlock_irq(&priv->ctx_lock);
         } else {
                 kfree(dev_ctx);
+                 /* delete all accumulated events */
+                cleanup_delayed_evets(priv);
         }
 }
 
@@ -341,6 +411,9 @@ void mlx5_core_event(struct mlx5_core_dev *dev, enum mlx5_dev_event event,
 
         spin_lock_irqsave(&priv->ctx_lock, flags);
 
+        if (priv->is_accum_events)
+                add_delayed_event(priv, dev, event, param);
+
         list_for_each_entry(dev_ctx, &priv->ctx_list, list)
                 if (dev_ctx->intf->event)
                         dev_ctx->intf->event(dev, dev_ctx->context, event, param);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
index 124c7c3c3a00..6dbd637b4e66 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
@@ -1343,6 +1343,9 @@ static int init_one(struct pci_dev *pdev,
         mutex_init(&dev->pci_status_mutex);
         mutex_init(&dev->intf_state_mutex);
 
+        INIT_LIST_HEAD(&priv->waiting_events_list);
+        priv->is_accum_events = false;
+
 #ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
         err = init_srcu_struct(&priv->pfault_srcu);
         if (err) {
diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index 88d6eb5b3a76..d26f18b39c4a 100644
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -647,6 +647,9 @@ struct mlx5_priv {
         struct list_head        ctx_list;
         spinlock_t              ctx_lock;
 
+        struct list_head        waiting_events_list;
+        bool                    is_accum_events;
+
         struct mlx5_flow_steering *steering;
         struct mlx5_mpfs        *mpfs;
         struct mlx5_eswitch     *eswitch;