i40e: synchronize nvmupdate command and adminq subtask

During NVM update, state machine gets into unrecoverable state because
i40e_clean_adminq_subtask can get scheduled after the admin queue
command but before other state variables are updated. This causes
incorrect input to i40e_nvmupd_check_wait_event and state transitions
don't happen.

This issue existed before but surfaced after commit 373149fc99a0
("i40e: Decrease the scope of rtnl lock")

This fix adds locking around admin queue command and update of
state variables so that adminq_subtask will have accurate information
whenever it gets scheduled.

Signed-off-by: Sudheer Mogilappagari <sudheer.mogilappagari@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_nvm.c

@@ -753,6 +753,11 @@ i40e_status i40e_nvmupd_command(struct i40e_hw *hw,
 		hw->nvmupd_state = I40E_NVMUPD_STATE_INIT;
 	}
 
+	/* Acquire lock to prevent race condition where adminq_task
+	 * can execute after i40e_nvmupd_nvm_read/write but before state
+	 * variables (nvm_wait_opcode, nvm_release_on_done) are updated
+	 */
+	mutex_lock(&hw->aq.arq_mutex);
 	switch (hw->nvmupd_state) {
 	case I40E_NVMUPD_STATE_INIT:
 		status = i40e_nvmupd_state_init(hw, cmd, bytes, perrno);
@@ -788,6 +793,7 @@ i40e_status i40e_nvmupd_command(struct i40e_hw *hw,
 		*perrno = -ESRCH;
 		break;
 	}
+	mutex_unlock(&hw->aq.arq_mutex);
 	return status;
 }