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authorDaniel Vetter <daniel.vetter@ffwll.ch>2013-11-03 20:46:34 +0100
committerDaniel Vetter <daniel.vetter@ffwll.ch>2014-04-23 10:32:33 +0200
commitfc8fd40eb29a936cc689d0008863d39a67741c67 (patch)
tree708dadf9ad9eb22a9a88cf12de128501c63d731c /include/drm/drmP.h
parent42b21049fc26513ca8e732f47559b1525b04a992 (diff)
downloadop-kernel-dev-fc8fd40eb29a936cc689d0008863d39a67741c67.zip
op-kernel-dev-fc8fd40eb29a936cc689d0008863d39a67741c67.tar.gz
drm: Rip out totally bogus vga_switcheroo->can_switch locking
So I just wanted to add a new field to struct drm_device and accidentally stumbled over something. According to comments dev->open_count is protected by dev->count_lock, but that's totally not the case. It's protected by drm_global_mutex. Unfortunately the vga switcheroo callbacks took this comment at face value. The problem is that we can't just take the drm_global_mutex because: - It would lead to a locking inversion with the driver load/unload paths. - It wouldn't actually protect anything, for that we'd need to wrap the entire vga switcheroo code in the drm_global_mutex. And I'm not sure whether that would actually solve anything. What we probably want is a try_to_grab_switcheroo reference kind of thing which is used in the driver's ->open callback. Then we could move all that ->can_switch madness into the vga switcheroo core where it really belongs. But since that would amount to real work take the easy way out and just add a comment. It's definitely not going to make anything worse since doing switcheroo state changes while restarting X just isn't recommended. Even though the delayed switching code does exactly that. v2: - Simplify the ->can_switch implementations more (Thierry) - Fix comment about the dev->open_count locking (Thierry) Cc: Thierry Reding <treding@nvidia.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> (v1) Reviewed-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'include/drm/drmP.h')
-rw-r--r--include/drm/drmP.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 9f1fb8d..a20d882 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1076,7 +1076,7 @@ struct drm_device {
/** \name Usage Counters */
/*@{ */
- int open_count; /**< Outstanding files open */
+ int open_count; /**< Outstanding files open, protected by drm_global_mutex. */
int buf_use; /**< Buffers in use -- cannot alloc */
atomic_t buf_alloc; /**< Buffer allocation in progress */
/*@} */
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