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| author | Michael Anthony Knyszek <mknyszek@google.com> | 2024-08-27 21:02:02 +0000 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2025-02-03 08:21:09 -0800 |
| commit | b25b5f3ff4e671aa4f5897c788137fe91f62cf57 (patch) | |
| tree | ef37f5db04b45dad5303ba33911a9ff133348705 /src/runtime/runtime1.go | |
| parent | 4f11d5879a01e64cb8bd59911bb205ffedd4f265 (diff) | |
| download | go-b25b5f3ff4e671aa4f5897c788137fe91f62cf57.tar.xz | |
runtime: fix GODEBUG=gccheckmark=1 and add smoke test
This change fixes GODEBUG=gccheckmark=1 which seems to have bit-rotted.
Because the root jobs weren't being reset, it wasn't doing anything.
Then, it turned out that checkmark mode would queue up noscan objects in
workbufs, which caused it to fail. Then it turned out checkmark mode was
broken with user arenas, since their heap arenas are not registered
anywhere. Then, it turned out that checkmark mode could just not run
properly if the goroutine's preemption flag was set (since
sched.gcwaiting is true during the STW). And lastly, it turned out that
async preemption could cause erroneous checkmark failures.
This change fixes all these issues and adds a simple smoke test to dist
to run the runtime tests under gccheckmark, which exercises all of these
issues.
Fixes #69074.
Fixes #69377.
Fixes #69376.
Change-Id: Iaa0bb7b9e63ed4ba34d222b47510d6292ce168bc
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/608915
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Diffstat (limited to 'src/runtime/runtime1.go')
| -rw-r--r-- | src/runtime/runtime1.go | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go index b47c589075..fb16f6daef 100644 --- a/src/runtime/runtime1.go +++ b/src/runtime/runtime1.go @@ -440,6 +440,23 @@ func parsedebugvars() { debug.malloc = (debug.inittrace | debug.sbrk) != 0 debug.profstackdepth = min(debug.profstackdepth, maxProfStackDepth) + // Disable async preemption in checkmark mode. The following situation is + // problematic with checkmark mode: + // + // - The GC doesn't mark object A because it is truly dead. + // - The GC stops the world, asynchronously preempting G1 which has a reference + // to A in its top stack frame + // - During the stop the world, we run the second checkmark GC. It marks the roots + // and discovers A through G1. + // - Checkmark mode reports a failure since there's a discrepancy in mark metadata. + // + // We could disable just conservative scanning during the checkmark scan, which is + // safe but makes checkmark slightly less powerful, but that's a lot more invasive + // than just disabling async preemption altogether. + if debug.gccheckmark > 0 { + debug.asyncpreemptoff = 1 + } + setTraceback(gogetenv("GOTRACEBACK")) traceback_env = traceback_cache } |