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25216afc9d("PCI: Add managed pcim_intx()") moved the allocation step for pci_intx()'s device resource from pcim_enable_device() to pcim_intx(). As before, pcim_enable_device() sets pci_dev.is_managed to true; and it is never set to false again. Due to the lifecycle of a struct pci_dev, it can happen that a second driver obtains the same pci_dev after a first driver ran. If one driver uses pcim_enable_device() and the other doesn't, this causes the other driver to run into managed pcim_intx(), which will try to allocate when called for the first time. Allocations might sleep, so calling pci_intx() while holding spinlocks becomes then invalid, which causes lockdep warnings and could cause deadlocks: ======================================================== WARNING: possible irq lock inversion dependency detected 6.11.0-rc6+ #59 Tainted: G W -------------------------------------------------------- CPU 0/KVM/1537 just changed the state of lock: ffffa0f0cff965f0 (&vdev->irqlock){-...}-{2:2}, at: vfio_intx_handler+0x21/0xd0 [vfio_pci_core] but this lock took another, HARDIRQ-unsafe lock in the past: (fs_reclaim){+.+.}-{0:0} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); local_irq_disable(); lock(&vdev->irqlock); lock(fs_reclaim); <Interrupt> lock(&vdev->irqlock); *** DEADLOCK *** Have pcim_enable_device()'s release function, pcim_disable_device(), set pci_dev.is_managed to false so that subsequent drivers using the same struct pci_dev do not implicitly run into managed code. Link: https://lore.kernel.org/r/20240905072556.11375-2-pstanner@redhat.com Fixes:25216afc9d("PCI: Add managed pcim_intx()") Reported-by: Alex Williamson <alex.williamson@redhat.com> Closes: https://lore.kernel.org/all/20240903094431.63551744.alex.williamson@redhat.com/ Suggested-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Philipp Stanner <pstanner@redhat.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Alex Williamson <alex.williamson@redhat.com> Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.