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Message-ID: <3a541265-f73d-6e3a-8a04-f0616d8ed961@nvidia.com>
Date: Sun, 20 Jun 2021 18:51:53 +0530
From: Vidya Sagar <vidyas@...dia.com>
To: Kishon Vijay Abraham I <kishon@...com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
Andrew Murray <amurray@...goodpenguin.co.uk>,
Bjorn Helgaas <bhelgaas@...gle.com>,
"Athani Nadeem Ladkhan" <nadeem@...ence.com>,
Tom Joseph <tjoseph@...ence.com>,
Manikanta Maddireddy <mmaddireddy@...dia.com>,
Om Prakash Singh <omp@...dia.com>,
Krishna Thota <kthota@...dia.com>
Subject: Re: [PATCH v2 2/5] PCI: endpoint: Replace spinlock with mutex
Hi Kishon,
Did you get time to look into it?
Thanks,
Vidya Sagar
On 6/11/2021 3:22 PM, Vidya Sagar wrote:
> 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@...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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