On Fri, Jul 30, 2021 at 07:06:26AM +0200, Greg Kroah-Hartman wrote: > On Thu, Jul 29, 2021 at 11:32:33PM +0000, Krzysztof Wilczyński wrote: > > Hello, > > > > At the moment, the dependency on iomem_get_mapping() that is currently > > used in the pci_create_resource_files() and pci_create_legacy_files() > > stops us from completely retiring the late_initcall() that is used to > > invoke pci_sysfs_init() when creating sysfs object for PCI devices. > > > > This dependency on iomem_get_mapping() stops us from retiring the > > late_initcall at the moment as when we convert dynamically added sysfs > > objects, that are primarily added in the pci_create_resource_files() and > > pci_create_legacy_files(), as these attributes are added before the VFS > > completes its initialisation, and since most of the PCI devices are > > typically enumerated in subsys_initcall this leads to a failure and an > > Oops related to iomem_get_mapping() access. > > > > See relevant conversations: > > https://lore.kernel.org/linux-pci/20210204165831.2703772-1-daniel.vetter@xxxxxxxx/ > > https://lore.kernel.org/linux-pci/20210313215747.GA2394467@bjorn-Precision-5520/ > > > > After some deliberation about the problem at hand, Dan Williams > > suggested a solution to the problem, as per: > > https://lore.kernel.org/linux-pci/CAPcyv4i0y_4cMGEpNVShLUyUk3nyWH203Ry3S87BqnDJE0Rmxg@xxxxxxxxxxxxxx/ > > > > The idea is to defer execution of the iomem_get_mapping() to only when > > the sysfs open callback is run, and thus removing the reliance of > > fs_initcalls to complete before any other sub-system that uses the > > iomem_get_mapping(). > > > > Currently, the PCI sub-system will benefit the most from this change > > allowing for it to complete the transition from dynamically created to > > static sysfs objects. > > > > This series aims to take Dan Williams' idea through the finish line. > > > > Related to: > > https://lore.kernel.org/linux-pci/20210527205845.GA1421476@bjorn-Precision-5520/ > > https://lore.kernel.org/linux-pci/20210507102706.7658-1-danijel.slivka@xxxxxxx/ > > https://lore.kernel.org/linux-pci/20200716110423.xtfyb3n6tn5ixedh@pali/ > > > > Krzysztof > > > > No objection from me on these, Bjorn, mind if I take them through my > driver core tree? That'd be great! Is your tree immutable? I'm hoping we can take advantage of this to get rid of pci_sysfs_init(), which will fix a race that people seem to be hitting frequently now [1]. I think Krzysztof is getting pretty close. [1] https://lore.kernel.org/r/m3eebg9puj.fsf@xxxxxxxxxxx
