mem-cache: Allow clean operations when block allocation fails

Block allocation can fail when there is an in-service MSHR that
operates on the victim block. This can happed due to:
* an upgrade operation: a request that needs a writable copy of the
  block finds a shared (non-writable) copy of the block in the cache
  and has allocates an MSHR for the pending upgrade operation, or
* a clean operation: a clean request finds a dirty copy of the block
  and allocates an MSHR for the pending clean operation.
This changes relaxes an assertion to allow for the 2nd case (cache
clean operations).

Change-Id: Ib51482160b5f2b3702ed744b0eac2029d34bc9d4
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/9021
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/mem/cache/cache.cc b/src/mem/cache/cache.cc
index 85c96772c..9ee935961 100644
--- a/src/mem/cache/cache.cc
+++ b/src/mem/cache/cache.cc
@@ -1826,10 +1826,10 @@ Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
         Addr repl_addr = tags->regenerateBlkAddr(blk);
         MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
         if (repl_mshr) {
-            // must be an outstanding upgrade request
+            // must be an outstanding upgrade or clean request
             // on a block we're about to replace...
-            assert(!blk->isWritable() || blk->isDirty());
-            assert(repl_mshr->needsWritable());
+            assert((!blk->isWritable() && repl_mshr->needsWritable()) ||
+                   repl_mshr->isCleaning());
             // too hard to replace block with transient state
             // allocation failed, block not inserted
             return nullptr;