[PATCH] dma-buf: fix and rework dma_buf_poll v7

[Michel Dänzer]

On 2021-07-20 3:11 p.m., Christian König wrote:
> Daniel pointed me towards this function and there are multiple obvious problems
> in the implementation.
> 
> First of all the retry loop is not working as intended. In general the retry
> makes only sense if you grab the reference first and then check the sequence
> values.
> 
> Then we should always also wait for the exclusive fence.
> 
> It's also good practice to keep the reference around when installing callbacks
> to fences you don't own.
> 
> And last the whole implementation was unnecessary complex and rather hard to
> understand which could lead to probably unexpected behavior of the IOCTL.
> 
> Fix all this by reworking the implementation from scratch. Dropping the
> whole RCU approach and taking the lock instead.
> 
> Only mildly tested and needs a thoughtful review of the code.
> 
> v2: fix the reference counting as well
> v3: keep the excl fence handling as is for stable
> v4: back to testing all fences, drop RCU
> v5: handle in and out separately
> v6: add missing clear of events
> v7: change coding style as suggested by Michel, drop unused variables
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> CC: stable at vger.kernel.org

Working fine with https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880

Tested-by: Michel Dänzer <mdaenzer at redhat.com>


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Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer