• Arnd Bergmann's avatar
    drm: kill BKL from common code · 58374713
    Arnd Bergmann authored
    This restricts the use of the big kernel lock to the i830 and i810
    device drivers. The three remaining users in common code (open, ioctl
    and release) get converted to a new mutex, the drm_global_mutex,
    making the locking stricter than the big kernel lock.
    
    This may have a performance impact, but only in those cases that
    currently don't use DRM_UNLOCKED flag in the ioctl list and would
    benefit from that anyway.
    
    The reason why i810 and i830 cannot use drm_global_mutex in their
    mmap functions is a lock-order inversion problem between the current
    use of the BKL and mmap_sem in these drivers. Since the BKL has
    release-on-sleep semantics, it's harmless but it would cause trouble
    if we replace the BKL with a mutex.
    
    Instead, these drivers get their own ioctl wrappers that take the
    BKL around every ioctl call and then set their own handlers as
    DRM_UNLOCKED.
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
    Cc: David Airlie <airlied@linux.ie>
    Cc: dri-devel@lists.freedesktop.org
    Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
    58374713
i830_drv.h 9.26 KB