Messages in this thread | | | Date | Fri, 1 Apr 2022 11:23:01 +0800 | Subject | Re: [PATCH RESEND] uio/uio_pci_generic: Introduce refcnt on open/release | From | Yao Hongbo <> |
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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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