Review Board 2.0.15

mem: Do not rely on the NeedsWritable flag for responses

Review Request #3263 - Created Dec. 29, 2015 and submitted

Andreas Hansson
Changeset 11287:7919581a74b4
mem: Do not rely on the NeedsWritable flag for responses

This patch removes the NeedsWritable flag for all responses, as it is
really only the request that needs a writable response. The response,
on the other hand, should in these cases always provide the line in a
writable state, as indicated by the hasSharers flag not being set.

When we send requests that has NeedsWritable set, the response will
always have the hasSharers flag not set. Additionally, there are cases
where the request did not have NeedsWritable set, and we still get a
writable response with the hasSharers flag not set. This never happens
on snoops, but is used by downstream caches to pass ownership

As part of this patch, the affected response types are updated, and
the snoop filter is similarly modified to check only the hasSharers
flag (as it should). A sanity check is also added to the packet class,
asserting that we never look at the NeedsWritable flag for responses.

No regressions are affected.

Review request changed
Updated (Dec. 31, 2015, 6:34 a.m.)

Status: Closed (submitted)