This avoid a dependency lock error. According to https://lwn.net/Articles/548909/ users of WW mutex API should avoid using different context. When a buffer is reserved with qxl_bo_reserve a ww_mutex_lock without context is used. However during qxl_draw_dirty_fb different locks with specific context are used. This is detected during a machine booting with a debug kernel with lock dependency checking enabled. Like many other function in this file to avoid this problem object pinning is used. Once the object is pinned is not necessary to keep the lock so it can be released avoiding the locking problem.
Signed-off-by: Frediano Ziglio fziglio@redhat.com --- drivers/gpu/drm/qxl/qxl_display.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c index a8dbb3e..656752d 100644 --- a/drivers/gpu/drm/qxl/qxl_display.c +++ b/drivers/gpu/drm/qxl/qxl_display.c @@ -241,6 +241,10 @@ static int qxl_crtc_page_flip(struct drm_crtc *crtc, ret = qxl_bo_reserve(bo, false); if (ret) return ret; + ret = qxl_bo_pin(bo, bo->type, NULL); + qxl_bo_unreserve(bo); + if (ret) + return ret;
qxl_draw_dirty_fb(qdev, qfb_src, bo, 0, 0, &norect, one_clip_rect, inc); @@ -254,7 +258,11 @@ static int qxl_crtc_page_flip(struct drm_crtc *crtc, } drm_vblank_put(dev, qcrtc->index);
- qxl_bo_unreserve(bo); + ret = qxl_bo_reserve(bo, false); + if (!ret) { + qxl_bo_unpin(bo); + qxl_bo_unreserve(bo); + }
return 0; }