Rocket Chip Generator (https://github.com/freechipsproject/rocket-chip)
82bbbf908d
The deadlock condition occurs when the acquire tracker attempts to request a writeback while the writeback unit is still busy and a voluntary release for the block to be written back is coming in. The voluntary release cannot be accepted because it conflicts with the acquire tracker. The acquire tracker can't merge the voluntary release because it is waiting to send the writeback. The writeback can't progress because the release it is waiting on is behind the voluntary release. The solution to this is to break the atomicity guarantee between the acquire tracker and the writeback unit. This allows the voluntary release tracker to take the voluntary release before the writeback unit accepts the conflicting request. This causes a potential race condition for the metadata array. The solution to this is to have the writeback unit re-read the metadata after accepting a request. |
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