These two patches fixes two lock dependencies issues.
Changes from v1: Sent a wrong patch.
Frediano Ziglio (2): drm/qxl: avoid buffer reservation in qxl_crtc_page_flip drm/qxl: avoid dependency lock
drivers/gpu/drm/qxl/qxl_display.c | 10 +++++++++- drivers/gpu/drm/qxl/qxl_release.c | 4 +--- 2 files changed, 10 insertions(+), 4 deletions(-)
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; }
qxl_bo_unref calls drm_gem_object_unreference_unlocked which locks dev->struct_mutex. However this lock could be already locked if the call came from qxl_gem_object_free. As we don't need to call qxl_bo_ref/qxl_bo_unref cause qxl_release_list_add will hold a reference by itself avoid to call them and the possible deadlock.
Signed-off-by: Frediano Ziglio fziglio@redhat.com --- drivers/gpu/drm/qxl/qxl_release.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c index b66ec33..4efa8e2 100644 --- a/drivers/gpu/drm/qxl/qxl_release.c +++ b/drivers/gpu/drm/qxl/qxl_release.c @@ -307,7 +307,7 @@ int qxl_alloc_surface_release_reserved(struct qxl_device *qdev, idr_ret = qxl_release_alloc(qdev, QXL_RELEASE_SURFACE_CMD, release); if (idr_ret < 0) return idr_ret; - bo = qxl_bo_ref(to_qxl_bo(entry->tv.bo)); + bo = to_qxl_bo(entry->tv.bo);
(*release)->release_offset = create_rel->release_offset + 64;
@@ -316,8 +316,6 @@ int qxl_alloc_surface_release_reserved(struct qxl_device *qdev, info = qxl_release_map(qdev, *release); info->id = idr_ret; qxl_release_unmap(qdev, *release, info); - - qxl_bo_unref(&bo); return 0; }
On 24.09.2015 15:25, Frediano Ziglio wrote:
qxl_bo_unref calls drm_gem_object_unreference_unlocked which locks dev->struct_mutex. However this lock could be already locked if the call came from qxl_gem_object_free. As we don't need to call qxl_bo_ref/qxl_bo_unref cause qxl_release_list_add will hold a reference by itself avoid to call them and the possible deadlock.
Signed-off-by: Frediano Ziglio fziglio@redhat.com
drivers/gpu/drm/qxl/qxl_release.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c index b66ec33..4efa8e2 100644 --- a/drivers/gpu/drm/qxl/qxl_release.c +++ b/drivers/gpu/drm/qxl/qxl_release.c @@ -307,7 +307,7 @@ int qxl_alloc_surface_release_reserved(struct qxl_device *qdev, idr_ret = qxl_release_alloc(qdev, QXL_RELEASE_SURFACE_CMD, release); if (idr_ret < 0) return idr_ret;
bo = qxl_bo_ref(to_qxl_bo(entry->tv.bo));
bo = to_qxl_bo(entry->tv.bo);(*release)->release_offset = create_rel->release_offset + 64;
@@ -316,8 +316,6 @@ int qxl_alloc_surface_release_reserved(struct qxl_device *qdev, info = qxl_release_map(qdev, *release); info->id = idr_ret; qxl_release_unmap(qdev, *release, info);
qxl_bo_unref(&bo);
Tested with: - Rawhide-Xfce-Live-1001.iso \ 4.3.0-0.rc3.git2.4.fc24.x86_64 + v2-1-2-drm-qxl-avoid-buffer-reservation-in-qxl_crtc_page_flip.patch + v2-2-2-drm-qxl-avoid-dependency-lock.patch
Tested-by: poma pomidorabelisima@gmail.com
dri-devel@lists.freedesktop.org
-
Frediano Ziglio -
poma