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SubjectRe: [PATCH RESEND] uio/uio_pci_generic: Introduce refcnt on open/release
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+ cc.

在 2022/4/1 上午4:30, Michael S. Tsirkin 写道:
> On Thu, Mar 31, 2022 at 10:23:52AM +0800, Yao Hongbo wrote:
>> If two userspace programs both open the PCI UIO fd, when one
>> of the program exits uncleanly, the other will cause IO hang
>> due to bus-mastering disabled.
>
> With two programs poking at the same device, how is this ever
> supposed to work even while both are alive?
>
>> It's a common usage for spdk/dpdk to use UIO. So, introduce refcnt
>> to avoid such problems.
>>
>> Fixes: 865a11f("uio/uio_pci_generic: Disable bus-mastering on release")
>> Reported-by: Xiu Yang <yangxiu.yx@alibaba-inc.com>
>> Signed-off-by: Yao Hongbo <yaohongbo@linux.alibaba.com>
>> ---
>> drivers/uio/uio_pci_generic.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
>> index e03f9b5..8add2cf 100644
>> --- a/drivers/uio/uio_pci_generic.c
>> +++ b/drivers/uio/uio_pci_generic.c
>> @@ -31,6 +31,7 @@
>> struct uio_pci_generic_dev {
>> struct uio_info info;
>> struct pci_dev *pdev;
>> + atomic_t refcnt;
>> };
>>
>> static inline struct uio_pci_generic_dev *
>> @@ -39,6 +40,14 @@ struct uio_pci_generic_dev {
>> return container_of(info, struct uio_pci_generic_dev, info);
>> }
>>
>> +static int open(struct uio_info *info, struct inode *inode)
>> +{
>> + struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
>> +
>> + atomic_inc(&gdev->refcnt);
>> + return 0;
>> +}
>> +
>> static int release(struct uio_info *info, struct inode *inode)
>> {
>> struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
>> @@ -51,7 +60,9 @@ static int release(struct uio_info *info, struct inode *inode)
>>  * Note that there's a non-zero chance doing this will wedge the device
>>  * at least until reset.
>> */
>> - pci_clear_master(gdev->pdev);
>> + if (atomic_dec_and_test(&gdev->refcnt))
>> + pci_clear_master(gdev->pdev);
>> +
>> return 0;
>> }
>>
>> @@ -92,8 +103,11 @@ static int probe(struct pci_dev *pdev,
>>
>> gdev->info.name = "uio_pci_generic";
>> gdev->info.version = DRIVER_VERSION;
>> + gdev->info.open = open;
>> gdev->info.release = release;
>> gdev->pdev = pdev;
>> + atomic_set(&gdev->refcnt, 0);
>> +
>> if (pdev->irq && (pdev->irq != IRQ_NOTCONNECTED)) {
>> gdev->info.irq = pdev->irq;
>> gdev->info.irq_flags = IRQF_SHARED;
>> --
>> 1.8.3.1

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