* [PATCH v2 1/2] drm/qxl: avoid buffer reservation in qxl_crtc_page_flip
2015-09-24 13:25 [PATCH v2 0/2] Dependency locks fixes for QXL driver Frediano Ziglio
@ 2015-09-24 13:25 ` Frediano Ziglio
2015-09-24 13:25 ` [PATCH v2 2/2] drm/qxl: avoid dependency lock Frediano Ziglio
1 sibling, 0 replies; 4+ messages in thread
From: Frediano Ziglio @ 2015-09-24 13:25 UTC (permalink / raw)
To: David Airlie; +Cc: spice-devel, dri-devel
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;
}
--
2.4.3
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^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v2 2/2] drm/qxl: avoid dependency lock
2015-09-24 13:25 [PATCH v2 0/2] Dependency locks fixes for QXL driver Frediano Ziglio
2015-09-24 13:25 ` [PATCH v2 1/2] drm/qxl: avoid buffer reservation in qxl_crtc_page_flip Frediano Ziglio
@ 2015-09-24 13:25 ` Frediano Ziglio
2015-10-01 14:01 ` poma
1 sibling, 1 reply; 4+ messages in thread
From: Frediano Ziglio @ 2015-09-24 13:25 UTC (permalink / raw)
To: David Airlie; +Cc: spice-devel, dri-devel
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;
}
--
2.4.3
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^ permalink raw reply related [flat|nested] 4+ messages in thread