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SubjectRe: [PATCH v2 2/5] PCI: endpoint: Replace spinlock with mutex
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Date
Hi Kishon,
Apologies for bringup it up this late.
I'm wondering if there was any issue which this patch tried to address?
Actually, "The pci_epc_ops is not intended to be invoked from interrupt
context" isn't true in case of Tegra194. We do call
dw_pcie_ep_init_notify() API from threaded irq service routine and it
eventually calls mutext_lock() of pci_epc_get_features() which is
reusulting in the following warning log.
BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:
Would like hear your comments on it.

Thanks,
Vidya Sagar

On 2/12/2020 4:55 PM, Kishon Vijay Abraham I wrote:
> External email: Use caution opening links or attachments
>
>
> The pci_epc_ops is not intended to be invoked from interrupt context.
> Hence replace spin_lock_irqsave and spin_unlock_irqrestore with
> mutex_lock and mutex_unlock respectively.
>
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
> drivers/pci/endpoint/pci-epc-core.c | 82 +++++++++++------------------
> include/linux/pci-epc.h | 6 +--
> 2 files changed, 34 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 2f6436599fcb..e51a12ed85bb 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -120,7 +120,6 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> u8 func_no)
> {
> const struct pci_epc_features *epc_features;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return NULL;
> @@ -128,9 +127,9 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> if (!epc->ops->get_features)
> return NULL;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> epc_features = epc->ops->get_features(epc, func_no);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return epc_features;
> }
> @@ -144,14 +143,12 @@ EXPORT_SYMBOL_GPL(pci_epc_get_features);
> */
> void pci_epc_stop(struct pci_epc *epc)
> {
> - unsigned long flags;
> -
> if (IS_ERR(epc) || !epc->ops->stop)
> return;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> epc->ops->stop(epc);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
> }
> EXPORT_SYMBOL_GPL(pci_epc_stop);
>
> @@ -164,7 +161,6 @@ EXPORT_SYMBOL_GPL(pci_epc_stop);
> int pci_epc_start(struct pci_epc *epc)
> {
> int ret;
> - unsigned long flags;
>
> if (IS_ERR(epc))
> return -EINVAL;
> @@ -172,9 +168,9 @@ int pci_epc_start(struct pci_epc *epc)
> if (!epc->ops->start)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->start(epc);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -193,7 +189,6 @@ int pci_epc_raise_irq(struct pci_epc *epc, u8 func_no,
> enum pci_epc_irq_type type, u16 interrupt_num)
> {
> int ret;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return -EINVAL;
> @@ -201,9 +196,9 @@ int pci_epc_raise_irq(struct pci_epc *epc, u8 func_no,
> if (!epc->ops->raise_irq)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->raise_irq(epc, func_no, type, interrupt_num);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -219,7 +214,6 @@ EXPORT_SYMBOL_GPL(pci_epc_raise_irq);
> int pci_epc_get_msi(struct pci_epc *epc, u8 func_no)
> {
> int interrupt;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return 0;
> @@ -227,9 +221,9 @@ int pci_epc_get_msi(struct pci_epc *epc, u8 func_no)
> if (!epc->ops->get_msi)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> interrupt = epc->ops->get_msi(epc, func_no);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> if (interrupt < 0)
> return 0;
> @@ -252,7 +246,6 @@ int pci_epc_set_msi(struct pci_epc *epc, u8 func_no, u8 interrupts)
> {
> int ret;
> u8 encode_int;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions ||
> interrupts > 32)
> @@ -263,9 +256,9 @@ int pci_epc_set_msi(struct pci_epc *epc, u8 func_no, u8 interrupts)
>
> encode_int = order_base_2(interrupts);
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->set_msi(epc, func_no, encode_int);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -281,7 +274,6 @@ EXPORT_SYMBOL_GPL(pci_epc_set_msi);
> int pci_epc_get_msix(struct pci_epc *epc, u8 func_no)
> {
> int interrupt;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return 0;
> @@ -289,9 +281,9 @@ int pci_epc_get_msix(struct pci_epc *epc, u8 func_no)
> if (!epc->ops->get_msix)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> interrupt = epc->ops->get_msix(epc, func_no);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> if (interrupt < 0)
> return 0;
> @@ -311,7 +303,6 @@ EXPORT_SYMBOL_GPL(pci_epc_get_msix);
> int pci_epc_set_msix(struct pci_epc *epc, u8 func_no, u16 interrupts)
> {
> int ret;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions ||
> interrupts < 1 || interrupts > 2048)
> @@ -320,9 +311,9 @@ int pci_epc_set_msix(struct pci_epc *epc, u8 func_no, u16 interrupts)
> if (!epc->ops->set_msix)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->set_msix(epc, func_no, interrupts - 1);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -339,17 +330,15 @@ EXPORT_SYMBOL_GPL(pci_epc_set_msix);
> void pci_epc_unmap_addr(struct pci_epc *epc, u8 func_no,
> phys_addr_t phys_addr)
> {
> - unsigned long flags;
> -
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return;
>
> if (!epc->ops->unmap_addr)
> return;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> epc->ops->unmap_addr(epc, func_no, phys_addr);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
> }
> EXPORT_SYMBOL_GPL(pci_epc_unmap_addr);
>
> @@ -367,7 +356,6 @@ int pci_epc_map_addr(struct pci_epc *epc, u8 func_no,
> phys_addr_t phys_addr, u64 pci_addr, size_t size)
> {
> int ret;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return -EINVAL;
> @@ -375,9 +363,9 @@ int pci_epc_map_addr(struct pci_epc *epc, u8 func_no,
> if (!epc->ops->map_addr)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->map_addr(epc, func_no, phys_addr, pci_addr, size);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -394,8 +382,6 @@ EXPORT_SYMBOL_GPL(pci_epc_map_addr);
> void pci_epc_clear_bar(struct pci_epc *epc, u8 func_no,
> struct pci_epf_bar *epf_bar)
> {
> - unsigned long flags;
> -
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions ||
> (epf_bar->barno == BAR_5 &&
> epf_bar->flags & PCI_BASE_ADDRESS_MEM_TYPE_64))
> @@ -404,9 +390,9 @@ void pci_epc_clear_bar(struct pci_epc *epc, u8 func_no,
> if (!epc->ops->clear_bar)
> return;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> epc->ops->clear_bar(epc, func_no, epf_bar);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
> }
> EXPORT_SYMBOL_GPL(pci_epc_clear_bar);
>
> @@ -422,7 +408,6 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no,
> struct pci_epf_bar *epf_bar)
> {
> int ret;
> - unsigned long irq_flags;
> int flags = epf_bar->flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions ||
> @@ -437,9 +422,9 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no,
> if (!epc->ops->set_bar)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, irq_flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->set_bar(epc, func_no, epf_bar);
> - spin_unlock_irqrestore(&epc->lock, irq_flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -460,7 +445,6 @@ int pci_epc_write_header(struct pci_epc *epc, u8 func_no,
> struct pci_epf_header *header)
> {
> int ret;
> - unsigned long flags;
>
> if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> return -EINVAL;
> @@ -468,9 +452,9 @@ int pci_epc_write_header(struct pci_epc *epc, u8 func_no,
> if (!epc->ops->write_header)
> return 0;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> ret = epc->ops->write_header(epc, func_no, header);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return ret;
> }
> @@ -487,8 +471,6 @@ EXPORT_SYMBOL_GPL(pci_epc_write_header);
> */
> int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf)
> {
> - unsigned long flags;
> -
> if (epf->epc)
> return -EBUSY;
>
> @@ -500,9 +482,9 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf)
>
> epf->epc = epc;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> list_add_tail(&epf->list, &epc->pci_epf);
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
>
> return 0;
> }
> @@ -517,15 +499,13 @@ EXPORT_SYMBOL_GPL(pci_epc_add_epf);
> */
> void pci_epc_remove_epf(struct pci_epc *epc, struct pci_epf *epf)
> {
> - unsigned long flags;
> -
> if (!epc || IS_ERR(epc) || !epf)
> return;
>
> - spin_lock_irqsave(&epc->lock, flags);
> + mutex_lock(&epc->lock);
> list_del(&epf->list);
> epf->epc = NULL;
> - spin_unlock_irqrestore(&epc->lock, flags);
> + mutex_unlock(&epc->lock);
> }
> EXPORT_SYMBOL_GPL(pci_epc_remove_epf);
>
> @@ -604,7 +584,7 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops,
> goto err_ret;
> }
>
> - spin_lock_init(&epc->lock);
> + mutex_init(&epc->lock);
> INIT_LIST_HEAD(&epc->pci_epf);
> ATOMIC_INIT_NOTIFIER_HEAD(&epc->notifier);
>
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 36644ccd32ac..9dd60f2e9705 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -88,7 +88,7 @@ struct pci_epc_mem {
> * @mem: address space of the endpoint controller
> * @max_functions: max number of functions that can be configured in this EPC
> * @group: configfs group representing the PCI EPC device
> - * @lock: spinlock to protect pci_epc ops
> + * @lock: mutex to protect pci_epc ops
> * @notifier: used to notify EPF of any EPC events (like linkup)
> */
> struct pci_epc {
> @@ -98,8 +98,8 @@ struct pci_epc {
> struct pci_epc_mem *mem;
> u8 max_functions;
> struct config_group *group;
> - /* spinlock to protect against concurrent access of EP controller */
> - spinlock_t lock;
> + /* mutex to protect against concurrent access of EP controller */
> + struct mutex lock;
> struct atomic_notifier_head notifier;
> };
>
> --
> 2.17.1
>

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