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authorChris Wilson <chris@chris-wilson.co.uk>2016-04-13 19:35:15 +0300
committerChris Wilson <chris@chris-wilson.co.uk>2016-04-14 12:45:40 +0300
commitaa9b78104fe3210758fa9e6c644e9a108d371e8b (patch)
treec254a0ac113c978d28f1caa4072691daf93457ac /drivers/gpu/drm/i915/intel_overlay.c
parentfcb5106d665879edbc1ebb6e1f1a67695954b81d (diff)
downloadlinux-aa9b78104fe3210758fa9e6c644e9a108d371e8b.tar.xz
drm/i915: Late request cancellations are harmful
Conceptually, each request is a record of a hardware transaction - we build up a list of pending commands and then either commit them to hardware, or cancel them. However, whilst building up the list of pending commands, we may modify state outside of the request and make references to the pending request. If we do so and then cancel that request, external objects then point to the deleted request leading to both graphical and memory corruption. The easiest example is to consider object/VMA tracking. When we mark an object as active in a request, we store a pointer to this, the most recent request, in the object. Then we want to free that object, we wait for the most recent request to be idle before proceeding (otherwise the hardware will write to pages now owned by the system, or we will attempt to read from those pages before the hardware is finished writing). If the request was cancelled instead, that wait completes immediately. As a result, all requests must be committed and not cancelled if the external state is unknown. All that remains of i915_gem_request_cancel() users are just a couple of extremely unlikely allocation failures, so remove the API entirely. A consequence of committing all incomplete requests is that we generate excess breadcrumbs and fill the ring much more often with dummy work. We have completely undone the outstanding_last_seqno optimisation. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93907 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> Cc: stable@vger.kernel.org Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1460565315-7748-16-git-send-email-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/intel_overlay.c')
-rw-r--r--drivers/gpu/drm/i915/intel_overlay.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index 6694e9230cd5..bcc3b6a016d8 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -247,7 +247,7 @@ static int intel_overlay_on(struct intel_overlay *overlay)
ret = intel_ring_begin(req, 4);
if (ret) {
- i915_gem_request_cancel(req);
+ i915_add_request_no_flush(req);
return ret;
}
@@ -290,7 +290,7 @@ static int intel_overlay_continue(struct intel_overlay *overlay,
ret = intel_ring_begin(req, 2);
if (ret) {
- i915_gem_request_cancel(req);
+ i915_add_request_no_flush(req);
return ret;
}
@@ -356,7 +356,7 @@ static int intel_overlay_off(struct intel_overlay *overlay)
ret = intel_ring_begin(req, 6);
if (ret) {
- i915_gem_request_cancel(req);
+ i915_add_request_no_flush(req);
return ret;
}
@@ -431,7 +431,7 @@ static int intel_overlay_release_old_vid(struct intel_overlay *overlay)
ret = intel_ring_begin(req, 2);
if (ret) {
- i915_gem_request_cancel(req);
+ i915_add_request_no_flush(req);
return ret;
}