Kyle Roarty has submitted this change. (
https://gem5-review.googlesource.com/c/public/gem5/+/34555 )
Change subject: gpu-compute: Fix deadlock in fetch_unit after branch
instruction
......................................................................
gpu-compute: Fix deadlock in fetch_unit after branch instruction
The following deadlock was occuring in fetch_unit w/timingSim:
1. exec() is called, a wave is ready to fetch, so it sets pendingFetch
2. A packet is sent to ITLB to fetch for that wave
3. The wave executes a branch, causing the fetch buffer to be cleared
4. The packet is handled, and fetch() is called. However, because the
fetch buffer was cleared, it returns doing nothing.
5. exec() gets called again, but the wave will never be scheduled to
fetch, as pendingFetch is still set to true.
This patch clears pendingFetch (and dropFetch) before returning in fetch()
when the fetch buffer has been cleared.
dropFetch needed to be cleared otherwise gem5 would crash.
Change-Id: Iccbac7defc4849c19e8b17aa2492da641defb772
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34555
Reviewed-by: Jason Lowe-Power <[email protected]>
Reviewed-by: Matt Sinclair <[email protected]>
Reviewed-by: Anthony Gutierrez <[email protected]>
Maintainer: Anthony Gutierrez <[email protected]>
Tested-by: kokoro <[email protected]>
---
M src/gpu-compute/fetch_unit.cc
1 file changed, 2 insertions(+), 0 deletions(-)
Approvals:
Jason Lowe-Power: Looks good to me, but someone else must approve
Anthony Gutierrez: Looks good to me, approved; Looks good to me, approved
Matt Sinclair: Looks good to me, but someone else must approve
kokoro: Regressions pass
diff --git a/src/gpu-compute/fetch_unit.cc b/src/gpu-compute/fetch_unit.cc
index 4e4259e..098b783 100644
--- a/src/gpu-compute/fetch_unit.cc
+++ b/src/gpu-compute/fetch_unit.cc
@@ -240,6 +240,8 @@
* pending, in the same cycle another instruction is trying to fetch.
*/
if
(!fetchBuf.at(wavefront->wfSlotId).isReserved(pkt->req->getVaddr())) {
+ wavefront->dropFetch = false;
+ wavefront->pendingFetch = false;
return;
}
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: Iccbac7defc4849c19e8b17aa2492da641defb772
Gerrit-Change-Number: 34555
Gerrit-PatchSet: 3
Gerrit-Owner: Kyle Roarty <[email protected]>
Gerrit-Assignee: Matthew Poremba <[email protected]>
Gerrit-Reviewer: Alexandru Duțu <[email protected]>
Gerrit-Reviewer: Anthony Gutierrez <[email protected]>
Gerrit-Reviewer: Jason Lowe-Power <[email protected]>
Gerrit-Reviewer: Kyle Roarty <[email protected]>
Gerrit-Reviewer: Matt Sinclair <[email protected]>
Gerrit-Reviewer: kokoro <[email protected]>
Gerrit-CC: Matthew Poremba <[email protected]>
Gerrit-MessageType: merged
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