iwlwifi: pcie: move rx workqueue initialization to iwl_trans_pcie_alloc()

Work queues cannot be allocated when a mutex is held because the mutex
may be in use and that would make it sleep.  Doing so generates the
following splat with 4.13+:

[   19.513298] ======================================================
[   19.513429] WARNING: possible circular locking dependency detected
[   19.513557] 4.13.0-rc5+ #6 Not tainted
[   19.513638] ------------------------------------------------------
[   19.513767] cpuhp/0/12 is trying to acquire lock:
[   19.513867]  (&tz->lock){+.+.+.}, at: [<ffffffff924afebb>] thermal_zone_get_temp+0x5b/0xb0
[   19.514047]
[   19.514047] but task is already holding lock:
[   19.514166]  (cpuhp_state){+.+.+.}, at: [<ffffffff91cc4baa>] cpuhp_thread_fun+0x3a/0x210
[   19.514338]
[   19.514338] which lock already depends on the new lock.

This lock dependency already existed with previous kernel versions,
but it was not detected until commit 49dfe2a6 ("cpuhotplug: Link
lock stacks for hotplug callbacks") was introduced.
Reported-by: David Weinehall <david.weinehall@intel.com>
Reported-by: Jiri Kosina <jikos@kernel.org>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/intel/iwlwifi/pcie/internal.h

@@ -787,6 +787,8 @@ int iwl_pci_fw_enter_d0i3(struct iwl_trans *trans);
 
 void iwl_pcie_enable_rx_wake(struct iwl_trans *trans, bool enable);
 
+void iwl_pcie_rx_allocator_work(struct work_struct *data);
+
 /* common functions that are used by gen2 transport */
 void iwl_pcie_apm_config(struct iwl_trans *trans);
 int iwl_pcie_prepare_card_hw(struct iwl_trans *trans);

drivers/net/wireless/intel/iwlwifi/pcie/rx.c

@@ -597,7 +597,7 @@ static void iwl_pcie_rx_allocator_get(struct iwl_trans *trans,
 	rxq->free_count += RX_CLAIM_REQ_ALLOC;
 }
 
-static void iwl_pcie_rx_allocator_work(struct work_struct *data)
+void iwl_pcie_rx_allocator_work(struct work_struct *data)
 {
 	struct iwl_rb_allocator *rba_p =
 		container_of(data, struct iwl_rb_allocator, rx_alloc);
@@ -900,10 +900,6 @@ static int _iwl_pcie_rx_init(struct iwl_trans *trans)
 			return err;
 	}
 	def_rxq = trans_pcie->rxq;
-	if (!rba->alloc_wq)
-		rba->alloc_wq = alloc_workqueue("rb_allocator",
-						WQ_HIGHPRI | WQ_UNBOUND, 1);
-	INIT_WORK(&rba->rx_alloc, iwl_pcie_rx_allocator_work);
 
 	spin_lock(&rba->lock);
 	atomic_set(&rba->req_pending, 0);
@@ -1017,10 +1013,6 @@ void iwl_pcie_rx_free(struct iwl_trans *trans)
 	}
 
 	cancel_work_sync(&rba->rx_alloc);
-	if (rba->alloc_wq) {
-		destroy_workqueue(rba->alloc_wq);
-		rba->alloc_wq = NULL;
-	}
 
 	iwl_pcie_free_rbs_pool(trans);
 

drivers/net/wireless/intel/iwlwifi/pcie/trans.c

@@ -1786,6 +1786,11 @@ void iwl_trans_pcie_free(struct iwl_trans *trans)
 		iwl_pcie_tx_free(trans);
 	iwl_pcie_rx_free(trans);
 
+	if (trans_pcie->rba.alloc_wq) {
+		destroy_workqueue(trans_pcie->rba.alloc_wq);
+		trans_pcie->rba.alloc_wq = NULL;
+	}
+
 	if (trans_pcie->msix_enabled) {
 		for (i = 0; i < trans_pcie->alloc_vecs; i++) {
 			irq_set_affinity_hint(
@@ -3169,6 +3174,10 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 		trans_pcie->inta_mask = CSR_INI_SET_MASK;
 	 }
 
+	trans_pcie->rba.alloc_wq = alloc_workqueue("rb_allocator",
+						   WQ_HIGHPRI | WQ_UNBOUND, 1);
+	INIT_WORK(&trans_pcie->rba.rx_alloc, iwl_pcie_rx_allocator_work);
+
 #ifdef CONFIG_IWLWIFI_PCIE_RTPM
 	trans->runtime_pm_mode = IWL_PLAT_PM_MODE_D0I3;
 #else