Changeset 11257:ba65669135cb
---------------------------
mem: Prevent Cache wrongly deleting requests

Cache wrongly deletes an in-use request when Cache handles snoopin timing mode.
The deletion happens when the _respond_ variable is false in handleSnoop
function.  The original attempt of this deletion is to delete the request
created in MSHR::handleSnoop where a request is created because isPendingDirty()
is false and pkt->isInvalidate() is true.  That is, the code assumes that: if
_respond_ is false, then the request must be created in the scenario described
previously so it can be safely deleted.

However, the assumption is not checked before deleting the request. As a result,
it wrongly deletes requests that are not created by MSHR. This patch uses a set
to hold all created requests in MSHR, and use it check the assumption before
deletion.
---
 src/mem/cache/cache.cc | 12 +++++++++---
 src/mem/cache/cache.hh |  3 ++-
 src/mem/cache/mshr.cc  |  4 ++++
 src/mem/cache/mshr.hh  |  3 +++
 4 files changed, 18 insertions(+), 4 deletions(-)

Hi, I upload a test case to produce this bug, please download test-case.tar.xz from https://goo.gl/BN477d.

After uncompressing the test-case, change directory into test-case.

Then please update the gem5 variable in run.sh script to point to your gem5.opt executable.

Then run ./run.sh to produce the bug.
As described in my commit, this bug is due to Cache wrongly deleted an in-use request when handling snoop target.

This patch fixes this bug by preventing Cache wrongly deleting requests.
Thanks,
Chun-Chen