• Chris Wilson's avatar
    dma-buf, drm, ion: Propagate error code from dma_buf_start_cpu_access() · 18b862dc
    Chris Wilson authored
    Drivers, especially i915.ko, can fail during the initial migration of a
    dma-buf for CPU access. However, the error code from the driver was not
    being propagated back to ioctl and so userspace was blissfully ignorant
    of the failure. Rendering corruption ensues.
    
    Whilst fixing the ioctl to return the error code from
    dma_buf_start_cpu_access(), also do the same for
    dma_buf_end_cpu_access().  For most drivers, dma_buf_end_cpu_access()
    cannot fail. i915.ko however, as most drivers would, wants to avoid being
    uninterruptible (as would be required to guarrantee no failure when
    flushing the buffer to the device). As userspace already has to handle
    errors from the SYNC_IOCTL, take advantage of this to be able to restart
    the syscall across signals.
    
    This fixes a coherency issue for i915.ko as well as reducing the
    uninterruptible hold upon its BKL, the struct_mutex.
    
    Fixes commit c11e391d
    Author: Daniel Vetter <daniel.vetter@ffwll.ch>
    Date:   Thu Feb 11 20:04:51 2016 -0200
    
        dma-buf: Add ioctls to allow userspace to flush
    
    Testcase: igt/gem_concurrent_blit/*dmabuf*interruptible
    Testcase: igt/prime_mmap_coherency/ioctl-errors
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Cc: Tiago Vignatti <tiago.vignatti@intel.com>
    Cc: Stéphane Marchesin <marcheu@chromium.org>
    Cc: David Herrmann <dh.herrmann@gmail.com>
    Cc: Sumit Semwal <sumit.semwal@linaro.org>
    Cc: Daniel Vetter <daniel.vetter@intel.com>
    CC: linux-media@vger.kernel.org
    Cc: dri-devel@lists.freedesktop.org
    Cc: linaro-mm-sig@lists.linaro.org
    Cc: intel-gfx@lists.freedesktop.org
    Cc: devel@driverdev.osuosl.org
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    Link: http://patchwork.freedesktop.org/patch/msgid/1458331359-2634-1-git-send-email-chris@chris-wilson.co.uk
    18b862dc
i915_gem_dmabuf.c 8.64 KB