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Subject[PATCH v2] iwlwifi: pcie: move rx workqueue initialization to iwl_trans_pcie_alloc()
From: Luca Coelho <luciano.coelho@intel.com>

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@intel.com>
Reported-by: Jiri Kosina <jikos@kernel.org>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
---
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
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