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mem: Fix bug relating to writebacks and prefetches

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Previously the code commented about an unhandled case where it might be
possible for a writeback to arrive after a prefetch was generated but
before it was sent to the memory system.  I hit that case.  Luckily
the prefetchSquash() logic already in the code handles dropping prefetch
request in certian circumstances.
This commit is contained in:
Mitch Hayenga 2014-12-23 09:31:18 -05:00
parent df82a2d003
commit 4acd4a2055
1 changed files with 4 additions and 8 deletions
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12
src/mem/cache/cache_impl.hh vendored
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@ -1892,12 +1892,6 @@ Cache<TagStore>::getTimingPacket()
BlkType *blk = tags->findBlock(mshr->addr, mshr->isSecure);
if (tgt_pkt->cmd == MemCmd::HardPFReq) {
// It might be possible for a writeback to arrive between
// the time the prefetch is placed in the MSHRs and when
// it's selected to send... if so, this assert will catch
// that, and then we'll have to figure out what to do.
assert(blk == NULL);
// We need to check the caches above us to verify that
// they don't have a copy of this block in the dirty state
// at the moment. Without this check we could get a stale
@ -1909,8 +1903,10 @@ Cache<TagStore>::getTimingPacket()
cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
// Check to see if the prefetch was squashed by an upper cache
if (snoop_pkt.prefetchSquashed()) {
DPRINTF(Cache, "Prefetch squashed by upper cache. "
// Or if a writeback arrived between the time the prefetch was
// placed in the MSHRs and when it was selected to send.
if (snoop_pkt.prefetchSquashed() || blk != NULL) {
DPRINTF(Cache, "Prefetch squashed by cache. "
"Deallocating mshr target %#x.\n", mshr->addr);
// Deallocate the mshr target