Re: [PATCH v2] iwlwifi: pcie: move rx workqueue initialization to iwl_trans_pcie_alloc()

[David Weinehall]

On Tue, Aug 22, 2017 at 10:37:29AM +0300, Luca Coelho wrote:
> From: Luca Coelho <luciano.coelho@xxxxxxxxx>
> 
> 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 49dfe2a67797 ("cpuhotplug: Link
> lock stacks for hotplug callbacks") was introduced.
> 
> Reported-by: David Weinehall <david.weinehall@xxxxxxxxx>
> Reported-by: Jiri Kosina <jikos@xxxxxxxxxx>
> Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>

With this patch I no longer get the lockdep warning,
and the driver seems to work just as well as before.

Thanks!

Tested-by: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx>

> ---
> In v2:
>    - updated the commit message to a new version, with a grammar fix
>      and the actual commit that exposed the problem;
> 
>  drivers/net/wireless/intel/iwlwifi/pcie/internal.h |  2 ++
>  drivers/net/wireless/intel/iwlwifi/pcie/rx.c       | 10 +---------
>  drivers/net/wireless/intel/iwlwifi/pcie/trans.c    |  9 +++++++++
>  3 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/internal.h b/drivers/net/wireless/intel/iwlwifi/pcie/internal.h
> index fa315d84e98e..a1ea9ef97ed9 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/internal.h
> +++ b/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);
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> index 351c4423125a..942736d3fa75 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> +++ b/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);
>  
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> index f95eec52508e..3927bbf04f72 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> +++ b/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
> -- 
> 2.14.1
>