Messages in this thread | | | Date | Tue, 14 Feb 2023 14:17:29 +0100 | From | Greg KH <> | Subject | Re: [PATCH] uio:uio_pci_generic:Don't clear master bit when the process does not exit |
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On Tue, Feb 14, 2023 at 09:21:57PM +0800, Su Weifeng wrote: > From: Weifeng Su <suweifeng1@huawei.com> > > The /dev/uioX device is used by multiple processes. The current behavior > is to clear the master bit when a process exits. This affects other > processes that use the device, resulting in command suspension and > timeout. This behavior cannot be sensed by the process itself. > The solution is to add the reference counting. The reference count is > self-incremented and self-decremented each time when the device open and > close. The master bit is cleared only when the last process exited. > > Signed-off-by: Weifeng Su <suweifeng1@huawei.com> > --- > drivers/uio/uio_pci_generic.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c > index e03f9b532..d36d3e08e 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; > + refcount_t dev_refc; > }; > > static inline struct uio_pci_generic_dev * > @@ -39,10 +40,22 @@ to_uio_pci_generic_dev(struct uio_info *info) > 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); > + > + if (gdev) > + refcount_inc(&gdev->dev_refc);
This flat out does not work, sorry.
You should never rely on trying to count open/release calls, just let the vfs layer handle that for us as it currently does so.
Think about what happens if you call dup() in userspace on a filehandle...
> + return 0; > +} > + > static int release(struct uio_info *info, struct inode *inode) > { > struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info); > > + if (gdev && refcount_dec_not_one(&gdev->dev_refc))
I don't think you actually tested this as it is impossible for gdev to ever be NULL.
sorry, but this patch is not correct.
greg k-h
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