mem: Pass shared downstream through caches

Information
Submitter:	Andreas Hansson
Repository:	gem5
Branch:	default
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Description

Changeset 10781:497ec32a8e7c
---------------------------
mem: Pass shared downstream through caches

This patch ensures that we pass on information about a packet being
shared (rather than exclusive), when forwarding a packet downstream.

Without this patch there is a risk that a downstream cache considers
the line exclusive when it really isn't.

Testing Done

I was initially slightly uneasy that, in the timing case, the sharing information could be out of date, as the cpu_pkt has been buffered in the MSHR for an indeterminate amount of time. I doubt there's any harm in conservatively assuming the block to still be shared even in the (rare) case that it no longer is, though, so I convinced myself that it's OK.

Andreas Hansson March 31, 2015, 12:25 a.m. (March 31, 2015, 12:25 a.m.)
```
I'll elaborate on this in the code comments.
```

Steve Reinhardt March 31, 2015, 9:37 a.m. (March 31, 2015, 9:37 a.m.)

Thanks. I already gave it a "ship it", since it was fine even before you expanded the comments.

Description:

~		Changeset 10781:06996c41b263
	~	Changeset 10781:497ec32a8e7c

		mem: Pass shared downstream through caches

		This patch ensures that we pass on information about a packet being
		shared (rather than exclusive), when forwarding a packet downstream.

		Without this patch there is a risk that a downstream cache considers
		the line exclusive when it really isn't.

Diff:

Revision 2 (+12)

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src/mem/cache/cache_impl.hh

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Changeset 10781:06996c41b263

Changeset 10781:497ec32a8e7c

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Status: Closed (submitted)