Am 26.02.2017 um 22:35 schrieb Daniel Vetter:
On Sun, Feb 19, 2017 at 10:32:43AM +0100, Christian König wrote:
Am 18.02.2017 um 23:50 schrieb Nicolai Hähnle:
From: Nicolai Hähnle <nicolai.haehnle@xxxxxxx>
The vm fault handler relies on the fact that the VMA owns a reference
to the BO. However, once mmap_sem is released, other tasks are free to
destroy the VMA, which can lead to the BO being freed. Fix two code
paths where that can happen, both related to vm fault retries.
Found via a lock debugging warning which flagged &bo->wu_mutex as
locked while being destroyed.
Fixes: cbe12e74ee4e ("drm/ttm: Allow vm fault retries")
Signed-off-by: Nicolai Hähnle <nicolai.haehnle@xxxxxxx>
Good catch! Patch is Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Since you have commit rights and all, care to push to drm-misc.git?
Do I have to use dim or could I just push the patches using standard git?
See my problem with installing an extra tool in my dev environment is
that I have 5+ hard disks setup from an image with all the neat stuff I
need. Distributing something new in there would be rather painful for me.
On the other hand I could just setup my laptop and use that one as a
bridge for pushing into drm-misc. That would work for single bug fixes
like this, but would break my usual development workflow.
Christian.
-Daniel
--
This does not fix the random memory corruption I've been seeing.
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index a6ed9d5..750733a 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -66,8 +66,11 @@ static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
goto out_unlock;
+ ttm_bo_reference(bo);
up_read(&vma->vm_mm->mmap_sem);
(void) fence_wait(bo->moving, true);
+ ttm_bo_unreserve(bo);
+ ttm_bo_unref(&bo);
goto out_unlock;
}
@@ -120,8 +123,10 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ ttm_bo_reference(bo);
up_read(&vma->vm_mm->mmap_sem);
(void) ttm_bo_wait_unreserved(bo);
+ ttm_bo_unref(&bo);
}
return VM_FAULT_RETRY;
@@ -166,6 +171,13 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
ret = ttm_bo_vm_fault_idle(bo, vma, vmf);
if (unlikely(ret != 0)) {
retval = ret;
+
+ if (retval == VM_FAULT_RETRY &&
+ !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ /* The BO has already been unreserved. */
+ return retval;
+ }
+
goto out_unlock;
}
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