net/mlx5: Set command entry semaphore up once got index free

Avoid a race where command work handler may fail to allocate command
entry index, by holding the command semaphore down till command entry
index is being freed.

Fixes: 410bd754 ("net/mlx5: Add retry mechanism to the command entry index allocation")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Eran Ben Elisha <eranbe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/cmd.c

@@ -148,8 +148,12 @@ static void cmd_ent_put(struct mlx5_cmd_work_ent *ent)
 	if (!refcount_dec_and_test(&ent->refcnt))
 		return;
 
-	if (ent->idx >= 0)
-		cmd_free_index(ent->cmd, ent->idx);
+	if (ent->idx >= 0) {
+		struct mlx5_cmd *cmd = ent->cmd;
+
+		cmd_free_index(cmd, ent->idx);
+		up(ent->page_queue ? &cmd->pages_sem : &cmd->sem);
+	}
 
 	cmd_free_ent(ent);
 }
@@ -1602,8 +1606,6 @@ static void mlx5_cmd_comp_handler(struct mlx5_core_dev *dev, u64 vec, bool force
 	vector = vec & 0xffffffff;
 	for (i = 0; i < (1 << cmd->log_sz); i++) {
 		if (test_bit(i, &vector)) {
-			struct semaphore *sem;
-
 			ent = cmd->ent_arr[i];
 
 			/* if we already completed the command, ignore it */
@@ -1626,10 +1628,6 @@ static void mlx5_cmd_comp_handler(struct mlx5_core_dev *dev, u64 vec, bool force
 			    dev->state == MLX5_DEVICE_STATE_INTERNAL_ERROR)
 				cmd_ent_put(ent);
 
-			if (ent->page_queue)
-				sem = &cmd->pages_sem;
-			else
-				sem = &cmd->sem;
 			ent->ts2 = ktime_get_ns();
 			memcpy(ent->out->first.data, ent->lay->out, sizeof(ent->lay->out));
 			dump_command(dev, ent, 0);
@@ -1683,7 +1681,6 @@ static void mlx5_cmd_comp_handler(struct mlx5_core_dev *dev, u64 vec, bool force
 				 */
 				complete(&ent->done);
 			}
-			up(sem);
 		}
 	}
 }