testing: integer divide by zero in predictN

[dmitshur]

Go version

go version devel go1.24-3ae00f5d29 Fri Dec 6 02:16:12 2024 +0000 darwin/arm64

Output of go env in your module/workspace:

$ go env -changed
GOFLAGS='-ldflags=-extldflags=-Wl,-no_warn_duplicate_libraries'  # workaround for go.dev/issue/67799

Details

$ go env
AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/gopher/Library/Caches/go-build'
GODEBUG=''
GOENV='/Users/gopher/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS='-ldflags=-extldflags=-Wl,-no_warn_duplicate_libraries'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/yn/rz8r25f10z5fmwdg34tz6z1c0000gn/T/go-build955700323=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/Users/gopher/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/gopher/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/gopher/gotip'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/Users/gopher/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/gopher/gotip/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='devel go1.24-3ae00f5d29 Fri Dec 6 02:16:12 2024 +0000'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

Ran all.bash at Go tip (commit 3ae00f5).

What did you see happen?

panic: runtime error: integer divide by zero

goroutine 574 gp=0x140001adc00 m=4 mp=0x14000088008 [running]:
panic({0x100db05c0?, 0x100f260a0?})
	/Users/gopher/gotip/src/runtime/panic.go:806 +0x154 fp=0x14000105ea0 sp=0x14000105df0 pc=0x100c06c04
runtime.panicdivide()
	/Users/gopher/gotip/src/runtime/panic.go:241 +0x48 fp=0x14000105ec0 sp=0x14000105ea0 pc=0x100bcdc58
testing.predictN(...)
	/Users/gopher/gotip/src/testing/benchmark.go:283
testing.(*B).stopOrScaleBLoop(0x14000276008)
	/Users/gopher/gotip/src/testing/benchmark.go:375 +0xdc fp=0x14000105ef0 sp=0x14000105ec0 pc=0x100c9a4ac
testing.(*B).loopSlowPath(0x140000a5f38?)
	/Users/gopher/gotip/src/testing/benchmark.go:400 +0x6c fp=0x14000105f10 sp=0x14000105ef0 pc=0x100c9a53c
testing.(*B).Loop(...)
	/Users/gopher/gotip/src/testing/benchmark.go:429
testing_test.TestBLoopHasResults.func1(0x14000276008)
	/Users/gopher/gotip/src/testing/benchmark_test.go:135 +0x58 fp=0x14000105f40 sp=0x14000105f10 pc=0x100d27a08
testing.(*B).runN(0x14000276008, 0x1)
	/Users/gopher/gotip/src/testing/benchmark.go:199 +0x130 fp=0x14000105f90 sp=0x14000105f40 pc=0x100c997a0
testing.(*B).run1.func1()
	/Users/gopher/gotip/src/testing/benchmark.go:221 +0x4c fp=0x14000105fd0 sp=0x14000105f90 pc=0x100c99dbc
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000105fd0 sp=0x14000105fd0 pc=0x100c0e844
created by testing.(*B).run1 in goroutine 573
	/Users/gopher/gotip/src/testing/benchmark.go:214 +0x90

[...]

FAIL	testing	0.612s

benchmark.go:283 is https://cs.opensource.google/go/go/+/master:src/testing/benchmark.go;l=283;drc=5213e1e56c17bde612398dac8a2996bf020fe542.

Details

panic: runtime error: integer divide by zero

goroutine 574 gp=0x140001adc00 m=4 mp=0x14000088008 [running]:
panic({0x100db05c0?, 0x100f260a0?})
	/Users/gopher/gotip/src/runtime/panic.go:806 +0x154 fp=0x14000105ea0 sp=0x14000105df0 pc=0x100c06c04
runtime.panicdivide()
	/Users/gopher/gotip/src/runtime/panic.go:241 +0x48 fp=0x14000105ec0 sp=0x14000105ea0 pc=0x100bcdc58
testing.predictN(...)
	/Users/gopher/gotip/src/testing/benchmark.go:283
testing.(*B).stopOrScaleBLoop(0x14000276008)
	/Users/gopher/gotip/src/testing/benchmark.go:375 +0xdc fp=0x14000105ef0 sp=0x14000105ec0 pc=0x100c9a4ac
testing.(*B).loopSlowPath(0x140000a5f38?)
	/Users/gopher/gotip/src/testing/benchmark.go:400 +0x6c fp=0x14000105f10 sp=0x14000105ef0 pc=0x100c9a53c
testing.(*B).Loop(...)
	/Users/gopher/gotip/src/testing/benchmark.go:429
testing_test.TestBLoopHasResults.func1(0x14000276008)
	/Users/gopher/gotip/src/testing/benchmark_test.go:135 +0x58 fp=0x14000105f40 sp=0x14000105f10 pc=0x100d27a08
testing.(*B).runN(0x14000276008, 0x1)
	/Users/gopher/gotip/src/testing/benchmark.go:199 +0x130 fp=0x14000105f90 sp=0x14000105f40 pc=0x100c997a0
testing.(*B).run1.func1()
	/Users/gopher/gotip/src/testing/benchmark.go:221 +0x4c fp=0x14000105fd0 sp=0x14000105f90 pc=0x100c99dbc
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000105fd0 sp=0x14000105fd0 pc=0x100c0e844
created by testing.(*B).run1 in goroutine 573
	/Users/gopher/gotip/src/testing/benchmark.go:214 +0x90

goroutine 1 gp=0x140000021c0 m=nil [chan receive]:
runtime.gopark(0x1400018c018?, 0x14000106978?, 0x9e?, 0xf8?, 0x107ab6948?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000106930 sp=0x14000106910 pc=0x100c06fe8
runtime.chanrecv(0x140000ba070, 0x14000106a37, 0x1)
	/Users/gopher/gotip/src/runtime/chan.go:664 +0x42c fp=0x140001069b0 sp=0x14000106930 pc=0x100ba190c
runtime.chanrecv1(0x100f312e0?, 0x100df0440?)
	/Users/gopher/gotip/src/runtime/chan.go:506 +0x14 fp=0x140001069e0 sp=0x140001069b0 pc=0x100ba14a4
testing.(*T).Run(0x14000003500, {0x100d3ff3b?, 0x14000106af8?}, 0x100de8b60)
	/Users/gopher/gotip/src/testing/testing.go:1831 +0x388 fp=0x14000106ac0 sp=0x140001069e0 pc=0x100ca8bd8
testing.runTests.func1(0x14000003500)
	/Users/gopher/gotip/src/testing/testing.go:2251 +0x40 fp=0x14000106b00 sp=0x14000106ac0 pc=0x100caab60
testing.tRunner(0x14000003500, 0x14000106c28)
	/Users/gopher/gotip/src/testing/testing.go:1764 +0xe4 fp=0x14000106b50 sp=0x14000106b00 pc=0x100ca7e74
testing.runTests(0x1400000c018, {0x100f2df00, 0x44, 0x44}, {0xaa138f239b5ab4a4?, 0x0?, 0x100f314c0?})
	/Users/gopher/gotip/src/testing/testing.go:2249 +0x3ec fp=0x14000106c50 sp=0x14000106b50 pc=0x100caaa7c
testing.(*M).Run(0x1400010a140)
	/Users/gopher/gotip/src/testing/testing.go:2114 +0x588 fp=0x14000106e80 sp=0x14000106c50 pc=0x100ca97d8
testing_test.TestMain(0x1400010a140)
	/Users/gopher/gotip/src/testing/testing_test.go:35 +0x4c fp=0x14000106ea0 sp=0x14000106e80 pc=0x100d2a46c
main.main()
	_testmain.go:197 +0x98 fp=0x14000106f40 sp=0x14000106ea0 pc=0x100d31088
runtime.main()
	/Users/gopher/gotip/src/runtime/proc.go:283 +0x284 fp=0x14000106fd0 sp=0x14000106f40 pc=0x100bd2464
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000106fd0 sp=0x14000106fd0 pc=0x100c0e844

goroutine 2 gp=0x14000002700 m=nil [force gc (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000060f90 sp=0x14000060f70 pc=0x100c06fe8
runtime.goparkunlock(...)
	/Users/gopher/gotip/src/runtime/proc.go:441
runtime.forcegchelper()
	/Users/gopher/gotip/src/runtime/proc.go:348 +0xb8 fp=0x14000060fd0 sp=0x14000060f90 pc=0x100bd27b8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000060fd0 sp=0x14000060fd0 pc=0x100c0e844
created by runtime.init.7 in goroutine 1
	/Users/gopher/gotip/src/runtime/proc.go:336 +0x24

goroutine 3 gp=0x14000002c40 m=nil [GC sweep wait]:
runtime.gopark(0x100f31101?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000061760 sp=0x14000061740 pc=0x100c06fe8
runtime.goparkunlock(...)
	/Users/gopher/gotip/src/runtime/proc.go:441
runtime.bgsweep(0x14000078000)
	/Users/gopher/gotip/src/runtime/mgcsweep.go:316 +0x108 fp=0x140000617b0 sp=0x14000061760 pc=0x100bbbee8
runtime.gcenable.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:204 +0x28 fp=0x140000617d0 sp=0x140000617b0 pc=0x100bafd78
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x140000617d0 sp=0x140000617d0 pc=0x100c0e844
created by runtime.gcenable in goroutine 1
	/Users/gopher/gotip/src/runtime/mgc.go:204 +0x6c

goroutine 4 gp=0x14000002e00 m=nil [runnable]:
runtime.gopark(0x10000?, 0x6553f100?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000061f60 sp=0x14000061f40 pc=0x100c06fe8
runtime.goparkunlock(...)
	/Users/gopher/gotip/src/runtime/proc.go:441
runtime.(*scavengerState).park(0x100f31540)
	/Users/gopher/gotip/src/runtime/mgcscavenge.go:425 +0x5c fp=0x14000061f90 sp=0x14000061f60 pc=0x100bb998c
runtime.bgscavenge(0x14000078000)
	/Users/gopher/gotip/src/runtime/mgcscavenge.go:658 +0xac fp=0x14000061fb0 sp=0x14000061f90 pc=0x100bb9f2c
runtime.gcenable.gowrap2()
	/Users/gopher/gotip/src/runtime/mgc.go:205 +0x28 fp=0x14000061fd0 sp=0x14000061fb0 pc=0x100bafd18
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000061fd0 sp=0x14000061fd0 pc=0x100c0e844
created by runtime.gcenable in goroutine 1
	/Users/gopher/gotip/src/runtime/mgc.go:205 +0xac

goroutine 5 gp=0x14000003340 m=nil [finalizer wait]:
runtime.gopark(0x140000605b8?, 0x100c07c74?, 0x1?, 0x5?, 0x100c38544?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000060590 sp=0x14000060570 pc=0x100c06fe8
runtime.runfinq()
	/Users/gopher/gotip/src/runtime/mfinal.go:196 +0x108 fp=0x140000607d0 sp=0x14000060590 pc=0x100baed78
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x140000607d0 sp=0x140000607d0 pc=0x100c0e844
created by runtime.createfing in goroutine 1
	/Users/gopher/gotip/src/runtime/mfinal.go:166 +0x80

goroutine 573 gp=0x14000003880 m=nil [runnable]:
runtime.gopark(0x1000583be?, 0x100ca7dc3?, 0xb8?, 0x8c?, 0x107a87978?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000108c70 sp=0x14000108c50 pc=0x100c06fe8
runtime.chanrecv(0x140000ba0e0, 0x0, 0x1)
	/Users/gopher/gotip/src/runtime/chan.go:664 +0x42c fp=0x14000108cf0 sp=0x14000108c70 pc=0x100ba190c
runtime.chanrecv1(0x100eebd88?, 0x0?)
	/Users/gopher/gotip/src/runtime/chan.go:506 +0x14 fp=0x14000108d20 sp=0x14000108cf0 pc=0x100ba14a4
testing.(*B).run1(0x14000276008)
	/Users/gopher/gotip/src/testing/benchmark.go:223 +0xa0 fp=0x14000108e20 sp=0x14000108d20 pc=0x100c999a0
testing.Benchmark(0x14000194060)
	/Users/gopher/gotip/src/testing/benchmark.go:912 +0xc0 fp=0x14000108e90 sp=0x14000108e20 pc=0x100c9c940
testing_test.TestBLoopHasResults(0x140000bc000)
	/Users/gopher/gotip/src/testing/benchmark_test.go:133 +0x70 fp=0x14000108f60 sp=0x14000108e90 pc=0x100d27890
testing.tRunner(0x140000bc000, 0x100de8b60)
	/Users/gopher/gotip/src/testing/testing.go:1764 +0xe4 fp=0x14000108fb0 sp=0x14000108f60 pc=0x100ca7e74
testing.(*T).Run.gowrap1()
	/Users/gopher/gotip/src/testing/testing.go:1823 +0x2c fp=0x14000108fd0 sp=0x14000108fb0 pc=0x100ca8cfc
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000108fd0 sp=0x14000108fd0 pc=0x100c0e844
created by testing.(*T).Run in goroutine 1
	/Users/gopher/gotip/src/testing/testing.go:1823 +0x374

goroutine 87 gp=0x140001a9c00 m=nil [chan receive]:
runtime.gopark(0x14000109e48?, 0x100ba0608?, 0x78?, 0x9e?, 0x1400007c300?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000109dd0 sp=0x14000109db0 pc=0x100c06fe8
runtime.chanrecv(0x1400022f110, 0x0, 0x1)
	/Users/gopher/gotip/src/runtime/chan.go:664 +0x42c fp=0x14000109e50 sp=0x14000109dd0 pc=0x100ba190c
runtime.chanrecv1(0x100f312e0?, 0x100df0440?)
	/Users/gopher/gotip/src/runtime/chan.go:506 +0x14 fp=0x14000109e80 sp=0x14000109e50 pc=0x100ba14a4
testing.(*T).Parallel(0x14000231880)
	/Users/gopher/gotip/src/testing/testing.go:1549 +0x1b0 fp=0x14000109f20 sp=0x14000109e80 pc=0x100ca7af0
testing.TestTRun.func11(0x14000231880)
	/Users/gopher/gotip/src/testing/sub_test.go:319 +0x20 fp=0x14000109f60 sp=0x14000109f20 pc=0x100cb3ce0
testing.tRunner(0x14000231880, 0x100de8e20)
	/Users/gopher/gotip/src/testing/testing.go:1764 +0xe4 fp=0x14000109fb0 sp=0x14000109f60 pc=0x100ca7e74
testing.(*T).Run.gowrap1()
	/Users/gopher/gotip/src/testing/testing.go:1823 +0x2c fp=0x14000109fd0 sp=0x14000109fb0 pc=0x100ca8cfc
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000109fd0 sp=0x14000109fd0 pc=0x100c0e844
created by testing.(*T).Run in goroutine 86
	/Users/gopher/gotip/src/testing/testing.go:1823 +0x374

goroutine 122 gp=0x140001ac000 m=nil [GC worker (idle)]:
runtime.gopark(0x1400005ff58?, 0x100ca7dc4?, 0xc4?, 0x7d?, 0x1400005ff50?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400005ff10 sp=0x1400005fef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400005ffb0 sp=0x1400005ff10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400005ffd0 sp=0x1400005ffb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400005ffd0 sp=0x1400005ffd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 123 gp=0x140001ac380 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027c710 sp=0x1400027c6f0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027c7b0 sp=0x1400027c710 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027c7d0 sp=0x1400027c7b0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027c7d0 sp=0x1400027c7d0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 121 gp=0x140001ac700 m=nil [GC worker (idle)]:
runtime.gopark(0x1400005f758?, 0x100ca7dc4?, 0xc4?, 0x7d?, 0x1400005f750?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400005f710 sp=0x1400005f6f0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400005f7b0 sp=0x1400005f710 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400005f7d0 sp=0x1400005f7b0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400005f7d0 sp=0x1400005f7d0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 124 gp=0x14000224380 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027cf10 sp=0x1400027cef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027cfb0 sp=0x1400027cf10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027cfd0 sp=0x1400027cfb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027cfd0 sp=0x1400027cfd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 125 gp=0x14000230540 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027d710 sp=0x1400027d6f0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027d7b0 sp=0x1400027d710 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027d7d0 sp=0x1400027d7b0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027d7d0 sp=0x1400027d7d0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 126 gp=0x140002308c0 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027df10 sp=0x1400027def0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027dfb0 sp=0x1400027df10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027dfd0 sp=0x1400027dfb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027dfd0 sp=0x1400027dfd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 127 gp=0x14000280000 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027e710 sp=0x1400027e6f0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027e7b0 sp=0x1400027e710 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027e7d0 sp=0x1400027e7b0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027e7d0 sp=0x1400027e7d0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 128 gp=0x140002801c0 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027ef10 sp=0x1400027eef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027efb0 sp=0x1400027ef10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027efd0 sp=0x1400027efb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027efd0 sp=0x1400027efd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 129 gp=0x14000280380 m=nil [GC worker (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400027f710 sp=0x1400027f6f0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400027f7b0 sp=0x1400027f710 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400027f7d0 sp=0x1400027f7b0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400027f7d0 sp=0x1400027f7d0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 130 gp=0x14000280540 m=nil [GC worker (idle)]:
runtime.gopark(0x16fd2067eb11d?, 0x1?, 0xb4?, 0xdc?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400022af10 sp=0x1400022aef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400022afb0 sp=0x1400022af10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400022afd0 sp=0x1400022afb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400022afd0 sp=0x1400022afd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 131 gp=0x14000280700 m=nil [GC worker (idle)]:
runtime.gopark(0x100f58500?, 0x1?, 0x64?, 0x19?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000228f10 sp=0x14000228ef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x14000228fb0 sp=0x14000228f10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x14000228fd0 sp=0x14000228fb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000228fd0 sp=0x14000228fd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 132 gp=0x140002808c0 m=nil [GC worker (idle)]:
runtime.gopark(0x100f58500?, 0x1?, 0x52?, 0x99?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400022df10 sp=0x1400022def0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400022dfb0 sp=0x1400022df10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400022dfd0 sp=0x1400022dfb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400022dfd0 sp=0x1400022dfd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 133 gp=0x14000280a80 m=nil [GC worker (idle)]:
runtime.gopark(0x16fd20684b403?, 0x1?, 0x9?, 0xc1?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x14000102f10 sp=0x14000102ef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x14000102fb0 sp=0x14000102f10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x14000102fd0 sp=0x14000102fb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x14000102fd0 sp=0x14000102fd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140

goroutine 134 gp=0x14000280c40 m=nil [GC worker (idle)]:
runtime.gopark(0x100de91a8?, 0x14000015d20?, 0x1b?, 0xa?, 0x0?)
	/Users/gopher/gotip/src/runtime/proc.go:435 +0xc8 fp=0x1400022cf10 sp=0x1400022cef0 pc=0x100c06fe8
runtime.gcBgMarkWorker(0x1400024bc00)
	/Users/gopher/gotip/src/runtime/mgc.go:1423 +0xdc fp=0x1400022cfb0 sp=0x1400022cf10 pc=0x100bb220c
runtime.gcBgMarkStartWorkers.gowrap1()
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x28 fp=0x1400022cfd0 sp=0x1400022cfb0 pc=0x100bb20f8
runtime.goexit({})
	/Users/gopher/gotip/src/runtime/asm_arm64.s:1260 +0x4 fp=0x1400022cfd0 sp=0x1400022cfd0 pc=0x100c0e844
created by runtime.gcBgMarkStartWorkers in goroutine 120
	/Users/gopher/gotip/src/runtime/mgc.go:1339 +0x140
FAIL	testing	0.612s

So far it only happened the one time, and doesn't trivially reproduce when running testing package tests on its own:

$ go test -count=10 testing
ok  	testing	17.086s

What did you expect to see?

All tests passing.

CC @JunyangShao, @prattmic.

[gabyhelp]

Related Issues

• runtime/pprof: panic: test timed out after 9m0s #52916 (closed)
• math/bits: TestDiv32PanicOverflow, fatal error: unexpected signal during runtime execution #37065 (closed)
• panic: runtime.errorString("integer divide by zero") #65867 (closed)
• runtime: integer divide by zero check doesn't work on ARM #5805 (closed)
• Test failure in test/finprofiled.go --- integer divide by zero #64153 (closed)
• test/zerodivide.go: all expected zerodivide panic errors are skipped #18421 (closed)
• cmd/compile: internal compiler error: panic during prove #26043 (closed)
• runtime: waitforsingleobject wait_failed #65255 (closed)
• cmd/compile: unneccesary 0 check in division #45928 (closed)
• go/constant, math/big: panic while constructing constant "1i/1E-612198397" #20227 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[dmitshur]

go test -count=1000 -run=^TestBLoopHasResults$ testing reliably reproduces this on this machine, a MacBook Pro with M4 Pro, macOS 15.1.1 (24B2091).

[Jorropo]

On linux/amd64 I can't reproduce by default.
Here are my clocksources preferences.

> cat /sys/devices/system/clocksource/clocksource0/current_clocksource 
tsc
> cat /sys/devices/system/clocksource/clocksource0/available_clocksource 
tsc hpet acpi_pm

Manually switching the clocksource to the less accurate acpi_pm still did not make it reproduce (is go calling tsc from userland ? I think the vdsos do.).
However if then from this worst clocksource I run a VM and I don't give it access to the tsc hardware, then it reproduce.

Looking through the code some codepaths sanitize the nanoseconds before calling predictN, others don't. I'll send a fix.

[dmitshur]

Also reproduces on an M1 Pro machine.

Looking through the code some codepaths sanitize the nanoseconds before calling predictN, others don't. I'll send a fix.

I did that locally (in B.stopOrScaleBLoop) and can confirm it stops it from reproducing. Thanks.

[gopherbot]

Change https://go.dev/cl/633419 mentions this issue: testing: fix divide by zero when benchmark is faster than OS's clock resolution