diff options
| -rw-r--r-- | src/mem/cache/base.cc | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/src/mem/cache/base.cc b/src/mem/cache/base.cc index f087618c7..f31fbaf03 100644 --- a/src/mem/cache/base.cc +++ b/src/mem/cache/base.cc @@ -1,5 +1,5 @@ /* - * Copyright (c) 2012-2013, 2018 ARM Limited + * Copyright (c) 2012-2013, 2018-2019 ARM Limited * All rights reserved. * * The license below extends only to copyright in the software and shall @@ -1263,6 +1263,31 @@ BaseCache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks, chatty_assert(!isReadOnly, "Should never see dirty snoop response " "in read-only cache %s\n", name()); + + } else if (pkt->cmd.isSWPrefetch() && pkt->needsWritable()) { + // All other copies of the block were invalidated and we + // have an exclusive copy. + + // The coherence protocol assumes that if we fetched an + // exclusive copy of the block, we have the intention to + // modify it. Therefore the MSHR for the PrefetchExReq has + // been the point of ordering and this cache has commited + // to respond to snoops for the block. + // + // In most cases this is true anyway - a PrefetchExReq + // will be followed by a WriteReq. However, if that + // doesn't happen, the block is not marked as dirty and + // the cache doesn't respond to snoops that has committed + // to do so. + // + // To avoid deadlocks in cases where there is a snoop + // between the PrefetchExReq and the expected WriteReq, we + // proactively mark the block as Dirty. + + blk->status |= BlkDirty; + + panic_if(!isReadOnly, "Prefetch exclusive requests from read-only " + "cache %s\n", name()); } } |