On Tue, Aug 15, 2023 at 03:50:31PM -0400, Alistair Francis wrote: > On Tue, Aug 15, 2023 at 11:11 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Tue, Aug 15, 2023 at 09:44:32AM -0400, Alistair Francis wrote: > > > On Sat, Aug 12, 2023 at 4:26 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Sat, Aug 12, 2023 at 10:15:26AM +0200, Lukas Wunner wrote: > > > > > On Thu, Aug 10, 2023 at 11:34:11AM -0400, Alistair Francis wrote: > > > > > > On Thu, Aug 10, 2023 at 3:34???AM Lukas Wunner <lukas@xxxxxxxxx> wrote: > > > > > > > On Wed, Aug 09, 2023 at 07:28:51PM -0400, Alistair Francis wrote: > > > > > > > > --- a/drivers/pci/pci-sysfs.c > > > > > > > > +++ b/drivers/pci/pci-sysfs.c > > > > > > > > @@ -1226,6 +1227,12 @@ static int pci_create_resource_files(struct pci_dev *pdev) > > > > > > > > int i; > > > > > > > > int retval; > > > > > > > > > > > > > > > > +#ifdef CONFIG_PCI_DOE > > > > > > > > + retval = doe_sysfs_init(pdev); > > > > > > > > + if (retval) > > > > > > > > + return retval; > > > > > > > > +#endif > > > > > > > > + > > > > > > > > > > > > > > The preferred way to expose PCI sysfs attributes nowadays is to add them > > > > > > > to pci_dev_attr_groups[] and use the ->is_visible callback to check > > > > > > > whether they're applicable to a particular pci_dev. The alternative > > > > > > > via pci_create_resource_files() has race conditions which I think > > > > > > > still haven't been fixed. Bjorn recommended the ->is_visible approach > > > > > > > in response to the most recent attempt to fix the race: > > > > > > > > > > > > > > https://lore.kernel.org/linux-pci/20230427161458.GA249886@bhelgaas/ > > > > > > > > > > > > The is_visible doen't seem to work in this case. > > > > > > > > > > > > AFAIK is_visible only applies to the attributes under the group. Which > > > > > > means that every PCIe device will see a `doe_protos` directory, no > > > > > > matter if DOE is supported. > > > > > > > > > > internal_create_group() in fs/sysfs/group.c does this: > > > > > > > > > > if (grp->name) { > > > > > ... > > > > > kn = kernfs_create_dir_ns(kobj->sd, grp->name, ... > > > > > > > > > > So I'm under the impression that if you set the ->name member of > > > > > struct attribute_group, the attributes in that group appear under > > > > > a directory of that name. > > > > > > > > > > In fact, the kernel-doc for struct attribute_group claims as much: > > > > > > > > > > * struct attribute_group - data structure used to declare an attribute group. > > > > > * @name: Optional: Attribute group name > > > > > * If specified, the attribute group will be created in > > > > > * a new subdirectory with this name. > > > > > > > > > > So I don't quite understand why you think that "every PCIe device will > > > > > see a `doe_protos` directory, no matter if DOE is supported"? > > > > > > > > > > Am I missing something? > > > > > > > > I think the issue might be that the directory will be created even if no > > > > attributes are present in it due to the is_visable() check not returning > > > > any valid files? > > > > > > Yes, that's what I'm seeing. I see the directory for all PCIe devices > > > > > > This is a WIP that I had: > > > https://github.com/alistair23/linux/commit/61925cd174c31386eaa7e51e3a1be606b38f847c > > > > > > > > > > > If so, I had a patch somewhere around here where I was trying to fix > > > > that up: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/commit/?h=debugfs_cleanup&id=f670945dfbaf353fe068544c31e3fa45575da5b5 > > > > but it didn't seem to work properly and kept crashing. I didn't spend > > > > much time on looking into it, but if this is an issue, I can work on > > > > fixing this properly. > > > > > > That patch sounds like it would fix the issue of empty directories > > > that I'm seeing. Do you mind fixing it up properly? > > > > I am currently unable to do so due to travel and stuff for a few weeks, > > sorry. Feel free to take it and fix the boot crash that is seen with it > > and make it part of your patch series if you can't wait that long. > > No worries. > > It's much harder than I first thought though. There are currently lots > of users who expect the group to remain even if empty, as they > dynamically add/merge properties later. Which is what we end up doing > for DOE as well > > I'll keep looking into this and see if I can figure something out. Yeah, now that I think about it, that's where stuff fell apart for me as well. We should be able to create the group and then only create the file when they are added/merged, so I bet I missed a codepath somewhere. > Would an .attr_is_visible() function pointer for struct > attribute_group something that the kernel would accept? Worst case, yes, that would be acceptable. But try to see where I messed up on the original patch, it should be able to be done automatically somehow... thanks, greg k-h
