runtime: SIGSEGV in allocNeedsZero on darwin

[bcmills]

#!watchflakes
post <- goos == "darwin" && log ~ `runtime\.\(\*mheap\)\.allocNeedsZero` && log ~ `SIGSEGV`

(Pulled out from #55167 (comment).)

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- goos == "darwin" && log ~ `runtime\.\(\*mheap\)\.allocNeedsZero` && log ~ `SIGSEGV`

2023-01-17 01:51 darwin-amd64-11_0 tools@8e949673 go@145dd384 TestGoplsSourceDoesNotCallTokenFileMethods (log)

fatal error: unexpected signal during runtime execution
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x10263f1]

runtime stack:
runtime.throw({0x12a17c8?, 0x2031?})
	/tmp/buildlet/go/src/runtime/panic.go:1047 +0x5d fp=0x7000077b5598 sp=0x7000077b5568 pc=0x1034f1d
runtime.sigpanic()
	/tmp/buildlet/go/src/runtime/signal_unix.go:821 +0x3e9 fp=0x7000077b55f8 sp=0x7000077b5598 pc=0x104bb49
runtime.(*mheap).allocNeedsZero(0xc004000000?, 0x7000077b5640?, 0x102b539?)
	/tmp/buildlet/go/src/runtime/mheap.go:1021 +0x71 fp=0x7000077b5618 sp=0x7000077b55f8 pc=0x10263f1
...
	/tmp/buildlet/go/src/runtime/sema.go:62 +0x27 fp=0xc0000d7878 sp=0xc0000d7840 pc=0x10655a7
sync.(*WaitGroup).Wait(0xc000107a58?)
	/tmp/buildlet/go/src/sync/waitgroup.go:116 +0x4b fp=0xc0000d78a0 sp=0xc0000d7878 pc=0x107152b
golang.org/x/tools/go/packages.(*loader).refine(0xc0001b4000, 0xc0001ba050)
	/tmp/buildlet/gopath/src/golang.org/x/tools/go/packages/packages.go:778 +0xdd7 fp=0xc0000d7b98 sp=0xc0000d78a0 pc=0x1229d77
golang.org/x/tools/go/packages.Load(0x12ef1e8?, {0xc000198080, 0x2, 0x2})
	/tmp/buildlet/gopath/src/golang.org/x/tools/go/packages/packages.go:266 +0x9c fp=0xc0000d7bd0 sp=0xc0000d7b98 pc=0x12280bc
golang.org/x/tools/gopls/internal/lsp/safetoken_test.TestGoplsSourceDoesNotCallTokenFileMethods(0xc000082ea0)
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/lsp/safetoken/safetoken_test.go:76 +0xc8 fp=0xc0000d7f70 sp=0xc0000d7bd0 pc=0x1230088
testing.tRunner(0xc000082ea0, 0x12a7a98)

2023-02-16 18:10 darwin-amd64-12_0 tools@ad4fc28a go@518889b3 x/tools/gopls/internal/regtest/diagnostics.TestIssue37978 (log)

fatal error: unexpected signal during runtime execution
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x100027f51]

runtime stack:
runtime.throw({0x100b341e9?, 0x1001155bd?})
	/tmp/buildlet/go/src/runtime/panic.go:1075 +0x5c fp=0x70000a7f5d98 sp=0x70000a7f5d68 pc=0x100036b5c
runtime.sigpanic()
	/tmp/buildlet/go/src/runtime/signal_unix.go:821 +0x3e9 fp=0x70000a7f5df8 sp=0x70000a7f5d98 pc=0x10004d3a9
runtime.(*mheap).allocNeedsZero(0xf7?, 0x10115de88?, 0xc002000000?)
	/tmp/buildlet/go/src/runtime/mheap.go:1021 +0x71 fp=0x70000a7f5e18 sp=0x70000a7f5df8 pc=0x100027f51
...
	/tmp/buildlet/go/src/runtime/chan.go:442 +0x12 fp=0xc0033a5d68 sp=0xc0033a5d40 pc=0x100006c92
testing.(*T).Run(0xc00349cd00, {0x100ae9102?, 0x27?}, 0xc002588690)
	/tmp/buildlet/go/src/testing/testing.go:1630 +0x405 fp=0xc0033a5e28 sp=0xc0033a5d68 pc=0x100127425
golang.org/x/tools/gopls/internal/lsp/regtest.(*Runner).Run(0xc000336d20, 0xc00349cd00, {0x100b4efc9, 0x7c}, 0x100c60f48, {0x0, 0x0, 0x10008dcaf?})
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/lsp/regtest/runner.go:171 +0x3f0 fp=0xc0033a5f20 sp=0xc0033a5e28 pc=0x1008f5d30
golang.org/x/tools/gopls/internal/lsp/regtest.Run(...)
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/lsp/regtest/regtest.go:55
golang.org/x/tools/gopls/internal/regtest/diagnostics.TestIssue37978(0xc0016dca80?)
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/regtest/diagnostics/diagnostics_test.go:163 +0x3d fp=0xc0033a5f70 sp=0xc0033a5f20 pc=0x1008fe0dd
testing.tRunner(0xc00349cd00, 0x100c60f50)

2023-02-16 19:20 darwin-amd64-nocgo tools@e5b99481 go@031401a7 TestLSP (log)

fatal error: unexpected signal during runtime execution
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1026e71]

runtime stack:
runtime.throw({0x198e00d?, 0xc000054638?})
	/tmp/buildlet/go/src/runtime/panic.go:1075 +0x5c fp=0x700008bf0db8 sp=0x700008bf0d88 pc=0x1035a7c
runtime.sigpanic()
	/tmp/buildlet/go/src/runtime/signal_unix.go:821 +0x3e9 fp=0x700008bf0e18 sp=0x700008bf0db8 pc=0x104c2c9
runtime.(*mheap).allocNeedsZero(0x1f?, 0x1ff?, 0xc008002000?)
	/tmp/buildlet/go/src/runtime/mheap.go:1021 +0x71 fp=0x700008bf0e38 sp=0x700008bf0e18 pc=0x1026e71
...
	/tmp/buildlet/go/src/runtime/chan.go:583 +0x44e fp=0xc000080db8 sp=0xc000080d28 pc=0x10060ae
runtime.chanrecv1(0x208d1e0?, 0x181e1e0?)
	/tmp/buildlet/go/src/runtime/chan.go:442 +0x12 fp=0xc000080de0 sp=0xc000080db8 pc=0x1005c32
testing.(*T).Run(0xc000288340, {0x194b50d?, 0x599?}, 0xc00028c090)
	/tmp/buildlet/go/src/testing/testing.go:1630 +0x405 fp=0xc000080ea0 sp=0xc000080de0 pc=0x11253e5
golang.org/x/tools/gopls/internal/lsp/tests.RunTests(0xc000288340, {0x194f0ce, 0x8}, 0x1, 0x1a9d040)
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/lsp/tests/tests.go:297 +0x12a fp=0xc000080f38 sp=0xc000080ea0 pc=0x17530aa
golang.org/x/tools/gopls/internal/lsp.TestLSP(0xc000288000?)
	/tmp/buildlet/gopath/src/golang.org/x/tools/gopls/internal/lsp/lsp_test.go:51 +0x2b fp=0xc000080f70 sp=0xc000080f38 pc=0x179b5cb
testing.tRunner(0xc000288340, 0x1a9d020)

— watchflakes

[mknyszek]

The stack trace implies loading a nil heapArena struct. I'm not sure how this could happen (for instance due to a race). I'll look into it.

[mknyszek]

I want to look into whether this is actually only happening on Darwin.

[prattmic]

I see it once on freebsd in 2021:

2021-10-13T18:15:48-40f82f8/freebsd-386-12_2