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This seems to create a locking inversion with object_name_lock. The lock is held by drm_prime_fd_to_handle when calling our xe_gem_prime_import hook, which might eventually go on to grab the dma-resv lock during the attach. However we also have the opposite locking order in xe_gem_create_ioctl which is holding the dma-resv lock when calling drm_gem_handle_create, which wants to eventually grab object_name_lock: -> #1 (reservation_ww_class_mutex){+.+.}-{3:3}: <4> [635.739288] lock_acquire+0x169/0x3d0 <4> [635.739294] __ww_mutex_lock.constprop.0+0x164/0x1e60 <4> [635.739300] ww_mutex_lock_interruptible+0x42/0x1a0 <4> [635.739305] drm_gem_shmem_pin+0x4b/0x140 [drm_shmem_helper] <4> [635.739317] dma_buf_dynamic_attach+0x101/0x430 <4> [635.739323] xe_gem_prime_import+0xcc/0x2e0 [xe] <4> [635.739499] drm_prime_fd_to_handle_ioctl+0x184/0x2e0 [drm] <4> [635.739594] drm_ioctl_kernel+0x16f/0x250 [drm] <4> [635.739693] drm_ioctl+0x35e/0x620 [drm] <4> [635.739789] __x64_sys_ioctl+0xb7/0xf0 <4> [635.739794] do_syscall_64+0x3c/0x90 <4> [635.739799] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 <4> [635.739805] -> #0 (&dev->object_name_lock){+.+.}-{3:3}: <4> [635.739813] check_prev_add+0x1ba/0x14a0 <4> [635.739818] __lock_acquire+0x203e/0x2ff0 <4> [635.739823] lock_acquire+0x169/0x3d0 <4> [635.739827] __mutex_lock+0x124/0x1310 <4> [635.739832] drm_gem_handle_create+0x32/0x50 [drm] <4> [635.739927] xe_gem_create_ioctl+0x1d3/0x550 [xe] <4> [635.740102] drm_ioctl_kernel+0x16f/0x250 [drm] <4> [635.740197] drm_ioctl+0x35e/0x620 [drm] <4> [635.740293] __x64_sys_ioctl+0xb7/0xf0 <4> [635.740297] do_syscall_64+0x3c/0x90 <4> [635.740302] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 <4> [635.740307] It looks like it should be safe to simply drop the dma-resv lock prior to publishing the object when calling drm_gem_handle_create. Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/743 Signed-off-by: Matthew Auld <matthew.auld@intel.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
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 Restructured Text 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.