runtime: using AVX-512 instruction without supporting CPUID flag(s) on MacOS hangs the Go runtime

[vsivsi]

What version of Go are you using (go version)?

$ go version
go version go1.15.5 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

MacOS 10.15.7

go env Output

$ go env
GO111MODULE=""

GOARCH="amd64"

GOBIN=""

GOCACHE="/Users/vsi/Library/Caches/go-build"

GOENV="/Users/vsi/Library/Application Support/go/env"

GOEXE=""

GOFLAGS=""

GOHOSTARCH="amd64"

GOHOSTOS="darwin"

GOINSECURE=""

GOMODCACHE="/Users/vsi/go/pkg/mod"

GONOPROXY="github.com/vsivsi"

GONOSUMDB="github.com/vsivsi"

GOOS="darwin"

GOPATH="/Users/vsi/go"

GOPRIVATE="github.com/vsivsi"

GOPROXY="https://proxy.golang.org,direct"

GOROOT="/usr/local/Cellar/go/1.15.5/libexec"

GOSUMDB="sum.golang.org"

GOTMPDIR=""

GOTOOLDIR="/usr/local/Cellar/go/1.15.5/libexec/pkg/tool/darwin_amd64"

GCCGO="gccgo"

AR="ar"

CC="clang"

CXX="clang++"

CGO_ENABLED="1"

GOMOD=""

CGO_CFLAGS="-g -O2"

CGO_CPPFLAGS=""

CGO_CXXFLAGS="-g -O2"

CGO_FFLAGS="-g -O2"

CGO_LDFLAGS="-g -O2"

PKG_CONFIG="pkg-config"

GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/kp/kjdr0ytx5z9djnq4ysl15x0h0000gn/T/go-build367056703=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Attempt to use Intel AVX-512 VPOPCNT family AVX-512 instructions in go assembler.

What did you expect to see?

Assembly code using these instruction should run properly on processors supporting them, and should generate a UD fault (SIGILL) and terminate when invoked on a CPU without support.

What did you see instead?

Go runtime hangs forever with 100% CPU utilization upon executing a VPOPCNT(B/W/D/Q) instruction on hardware that doesn't support it. Tested running on a MacPro (2019) with 2.7 GHz 24-Core Intel Xeon W CPU (Xeon W-3265M)

$ sysctl machdep.cpu.leaf7_features
machdep.cpu.leaf7_features: RDWRFSGS TSC_THREAD_OFFSET BMI1 AVX2 FDPEO SMEP BMI2 ERMS INVPCID PQM FPU_CSDS MPX PQE AVX512F AVX512DQ RDSEED ADX SMAP CLFSOPT CLWB IPT AVX512CD AVX512BW AVX512VL PKU AVX512VNNI MDCLEAR IBRS STIBP L1DF ACAPMSR SSBD

Note, this processor does not include AVX512_BITALG or AVX512_VPOPCNTDQ, which are required for VPOPCNT(B/W) and VPOPCNT(D/Q) respectively. For a summary of the VPOPCNT support matrix, see: https://github.com/HJLebbink/asm-dude/wiki/VPOPCNT

The Intel processor documentation says that attempting to run such AVX512 instructions when the supporting feature CPUID flags are not set should result in raising a #UD exception. As expected, directly executing the amd64 UD2 instruction causes the go runtime to abort with SIGILL: illegal instruction. But when unsupported, these AVX512 instructions cause the runtime to hang in a tight loop of some kind, which doesn't seem to be consistent or correct behavior.

Here is a dump from a process sample of the hung go runtime process resulting from the repro below.

/usr/bin/sample Output

Sampling process 40325 for 3 seconds with 1 millisecond of run time between samples
Sampling completed, processing symbols...
Analysis of sampling vpopcntw (pid 40325) every 1 millisecond
Process:         vpopcntw [40325]
Path:            /Users/USER/*/vpopcntw
Load Address:    0x1000000
Identifier:      vpopcntw
Version:         ???
Code Type:       X86-64
Parent Process:  zsh [37987]
Date/Time:       2020-11-16 15:50:45.036 -0800

Launch Time:     2020-11-16 15:50:29.269 -0800

OS Version:      Mac OS X 10.15.7 (19H15)

Report Version:  7

Analysis Tool:   /usr/bin/sample
Physical footprint:         1732K

Physical footprint (peak):  1732K
Call graph:

2819 Thread_355890   DispatchQueue_1: com.apple.main-thread  (serial)

+ 2816 ???  (in )  [0xc00009e7d0]

+ ! 2816 main.popcnt  (in vpopcntw) + 0  [0x105c8e0]

+ 3 runtime.main  (in vpopcntw) + 521  [0x102ee69]

+   3 0x0

+     2 _sigtramp  (in libsystem_platform.dylib) + 0  [0x7fff685985e0]

+     1 _sigtramp  (in libsystem_platform.dylib) + 29  [0x7fff685985fd]

+       1 runtime.sigtramp  (in vpopcntw) + 51  [0x105aeb3]

+         1 ???  (in )  [0xc000000480]

+           1 runtime.setg  (in vpopcntw) + 5  [0x1059405]

2819 Thread_355892

+ 2819 thread_start  (in libsystem_pthread.dylib) + 15  [0x7fff6859fb8b]

+   2819 runtime.mstart_stub  (in vpopcntw) + 46  [0x105b14e]

+     2819 runtime.mstart  (in vpopcntw) + 102  [0x10316a6]

+       2819 runtime.mstart1  (in vpopcntw) + 200  [0x1031788]

+         2818 runtime.sysmon  (in vpopcntw) + 173  [0x10399ed]

+         ! 2818 runtime.usleep  (in vpopcntw) + 49  [0x1047dd1]

+         !   2818 runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]

+         !     2818 runtime.usleep_trampoline  (in vpopcntw) + 11  [0x105b02b]

+         !       2818 usleep  (in libsystem_c.dylib) + 53  [0x7fff68466de4]

+         !         2818 nanosleep  (in libsystem_c.dylib) + 196  [0x7fff68466eea]

+         !           2816 __semwait_signal  (in libsystem_kernel.dylib) + 10  [0x7fff684e3756]

+         !           1 cerror  (in libsystem_kernel.dylib) + 20  [0x7fff684e2241]

+         !           : 1 cerror_nocancel  (in libsystem_kernel.dylib) + 0  [0x7fff684e1629]

+         !           1 cerror  (in libsystem_kernel.dylib) + 0  [0x7fff684e222d]

+         1 runtime.sysmon  (in vpopcntw) + 433  [0x1039af1]

+           1 runtime.retake  (in vpopcntw) + 518  [0x103a0e6]

+             1 runtime.preemptone  (in vpopcntw) + 165  [0x103a2a5]

+               1 runtime.preemptM  (in vpopcntw) + 135  [0x103f307]

+                 1 runtime.pthread_kill  (in vpopcntw) + 49  [0x1047b11]

+                   1 runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]

+                     1 runtime.pthread_kill_trampoline  (in vpopcntw) + 16  [0x105b330]

+                       1 pthread_kill  (in libsystem_pthread.dylib) + 179  [0x7fff685a3d65]

2819 Thread_355893

+ 2819 runtime.mcall  (in vpopcntw) + 91  [0x105799b]

+   2819 runtime.park_m  (in vpopcntw) + 157  [0x103571d]

+     2819 runtime.schedule  (in vpopcntw) + 110  [0x1034f0e]

+       2819 runtime.startlockedm  (in vpopcntw) + 133  [0x1033785]

+         2819 runtime.stopm  (in vpopcntw) + 197  [0x1032d25]

+           2819 runtime.notesleep  (in vpopcntw) + 231  [0x1009387]

+             2819 runtime.semasleep  (in vpopcntw) + 141  [0x102972d]

+               2819 runtime.pthread_cond_wait  (in vpopcntw) + 57  [0x1048459]

+                 2819 runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]

+                   2819 runtime.pthread_cond_wait_trampoline  (in vpopcntw) + 16  [0x105b2b0]

+                     2819 _pthread_cond_wait  (in libsystem_pthread.dylib) + 698  [0x7fff685a4425]

+                       2819 __psynch_cvwait  (in libsystem_kernel.dylib) + 10  [0x7fff684e3882]

2819 Thread_355894

+ 2819 runtime.mcall  (in vpopcntw) + 91  [0x105799b]

+   2819 runtime.park_m  (in vpopcntw) + 157  [0x103571d]

+     2819 runtime.schedule  (in vpopcntw) + 110  [0x1034f0e]

+       2819 runtime.startlockedm  (in vpopcntw) + 133  [0x1033785]

+         2819 runtime.stopm  (in vpopcntw) + 197  [0x1032d25]

+           2819 runtime.notesleep  (in vpopcntw) + 231  [0x1009387]

+             2819 runtime.semasleep  (in vpopcntw) + 141  [0x102972d]

+               2819 runtime.pthread_cond_wait  (in vpopcntw) + 57  [0x1048459]

+                 2819 runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]

+                   2819 runtime.pthread_cond_wait_trampoline  (in vpopcntw) + 16  [0x105b2b0]

+                     2819 _pthread_cond_wait  (in libsystem_pthread.dylib) + 698  [0x7fff685a4425]

+                       2819 __psynch_cvwait  (in libsystem_kernel.dylib) + 10  [0x7fff684e3882]

2819 Thread_355895

2819 thread_start  (in libsystem_pthread.dylib) + 15  [0x7fff6859fb8b]

2819 runtime.mstart_stub  (in vpopcntw) + 46  [0x105b14e]

2819 runtime.mstart  (in vpopcntw) + 102  [0x10316a6]

2819 runtime.mstart1  (in vpopcntw) + 147  [0x1031753]

2819 runtime.schedule  (in vpopcntw) + 727  [0x1035177]

2819 runtime.findrunnable  (in vpopcntw) + 2687  [0x10344ff]

2819 runtime.stopm  (in vpopcntw) + 197  [0x1032d25]

2819 runtime.notesleep  (in vpopcntw) + 231  [0x1009387]

2819 runtime.semasleep  (in vpopcntw) + 141  [0x102972d]

2819 runtime.pthread_cond_wait  (in vpopcntw) + 57  [0x1048459]

2819 runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]

2819 runtime.pthread_cond_wait_trampoline  (in vpopcntw) + 16  [0x105b2b0]

2819 _pthread_cond_wait  (in libsystem_pthread.dylib) + 698  [0x7fff685a4425]

2819 __psynch_cvwait  (in libsystem_kernel.dylib) + 10  [0x7fff684e3882]
Total number in stack (recursive counted multiple, when >=5):

5       runtime.asmcgocall  (in vpopcntw) + 173  [0x10593ed]
Sort by top of stack, same collapsed (when >= 5):

__psynch_cvwait  (in libsystem_kernel.dylib)        8457

__semwait_signal  (in libsystem_kernel.dylib)        2816

main.popcnt  (in vpopcntw)        2816
Binary Images:

0x1000000 -          0x10c61ee +vpopcntw (???) /Users/*/vpopcntw

0xd52f000 -          0xd5c0f47  dyld (750.6) <1D318D60-C9B0-3511-BE9C-82AFD2EF930D> /usr/lib/dyld

0x7fff2a0cc000 -     0x7fff2a0ccfff  com.apple.Accelerate (1.11 - Accelerate 1.11) <4F9977AE-DBDB-3A16-A536-AC1F9938DCDD> /System/Library/Frameworks/Accelerate.framework/Versions/A/Accelerate

0x7fff2a0e4000 -     0x7fff2a73afff  com.apple.vImage (8.1 - 524.2.1)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vImage.framework/Versions/A/vImage

0x7fff2a73b000 -     0x7fff2a9a2ff7  libBLAS.dylib (1303.60.1)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib

0x7fff2a9a3000 -     0x7fff2ae76fef  libBNNS.dylib (144.100.2) <99C61C48-B14C-3DA6-8C31-6BF72DA0A3A9> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBNNS.dylib

0x7fff2ae77000 -     0x7fff2b212fff  libLAPACK.dylib (1303.60.1) <5E3E3867-50C3-3E6A-9A2E-007CE77A4641> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib

0x7fff2b213000 -     0x7fff2b228fec  libLinearAlgebra.dylib (1303.60.1) <3D433800-0099-33E0-8C81-15F83247B2C9> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLinearAlgebra.dylib

0x7fff2b229000 -     0x7fff2b22eff3  libQuadrature.dylib (7) <371F36A7-B12F-363E-8955-F24F7C2048F6> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libQuadrature.dylib

0x7fff2b22f000 -     0x7fff2b29ffff  libSparse.dylib (103)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libSparse.dylib

0x7fff2b2a0000 -     0x7fff2b2b2fef  libSparseBLAS.dylib (1303.60.1)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libSparseBLAS.dylib

0x7fff2b2b3000 -     0x7fff2b48afd7  libvDSP.dylib (735.140.1)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libvDSP.dylib

0x7fff2b48b000 -     0x7fff2b54dfef  libvMisc.dylib (735.140.1) <3601FDE3-B142-398D-987D-8151A51F0A96> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libvMisc.dylib

0x7fff2b54e000 -     0x7fff2b54efff  com.apple.Accelerate.vecLib (3.11 - vecLib 3.11)  /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/vecLib

0x7fff2ccb4000 -     0x7fff2d043ffa  com.apple.CFNetwork (1128.0.1 - 1128.0.1) <07F9CA9C-B954-3EA0-A710-3122BFF9F057> /System/Library/Frameworks/CFNetwork.framework/Versions/A/CFNetwork

0x7fff2e445000 -     0x7fff2e8c4feb  com.apple.CoreFoundation (6.9 - 1677.104)  /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation

0x7fff2f82d000 -     0x7fff2f82dfff  com.apple.CoreServices (1069.24 - 1069.24)  /System/Library/Frameworks/CoreServices.framework/Versions/A/CoreServices

0x7fff2f82e000 -     0x7fff2f8b3fff  com.apple.AE (838.1 - 838.1) <2E5FD5AE-8A7F-353F-9BD1-0241F3586181> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/AE.framework/Versions/A/AE

0x7fff2f8b4000 -     0x7fff2fb95ff7  com.apple.CoreServices.CarbonCore (1217 - 1217)  /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CarbonCore.framework/Versions/A/CarbonCore

0x7fff2fb96000 -     0x7fff2fbe3ffd  com.apple.DictionaryServices (1.2 - 323.6) <26B70C82-25BC-353A-858F-945B14C803A2> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/DictionaryServices.framework/Versions/A/DictionaryServices

0x7fff2fbe4000 -     0x7fff2fbecff7  com.apple.CoreServices.FSEvents (1268.100.1 - 1268.100.1)  /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/FSEvents.framework/Versions/A/FSEvents

0x7fff2fbed000 -     0x7fff2fe27ff6  com.apple.LaunchServices (1069.24 - 1069.24) <9A5359D9-9148-3B18-B868-56A9DA5FB60C> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/LaunchServices

0x7fff2fe28000 -     0x7fff2fec0ff1  com.apple.Metadata (10.7.0 - 2076.7) <0973F7E5-D58C-3574-A3CE-4F12CAC2D4C7> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/Metadata.framework/Versions/A/Metadata

0x7fff2fec1000 -     0x7fff2feeefff  com.apple.CoreServices.OSServices (1069.24 - 1069.24) <0E4F48AD-402C-3E9D-9CA9-6DD9479B28F9> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/OSServices.framework/Versions/A/OSServices

0x7fff2feef000 -     0x7fff2ff56fff  com.apple.SearchKit (1.4.1 - 1.4.1) <2C5E1D85-E8B1-3DC5-91B9-E3EDB48E9369> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/SearchKit.framework/Versions/A/SearchKit

0x7fff2ff57000 -     0x7fff2ff7bff5  com.apple.coreservices.SharedFileList (131.4 - 131.4) <02DE0D56-E371-3EF5-9BC1-FA435451B412> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/SharedFileList.framework/Versions/A/SharedFileList

0x7fff307c1000 -     0x7fff307c7fff  com.apple.DiskArbitration (2.7 - 2.7) <0BBBB6A6-604D-368B-9943-50B8CE75D51D> /System/Library/Frameworks/DiskArbitration.framework/Versions/A/DiskArbitration

0x7fff30b02000 -     0x7fff30ec7fff  com.apple.Foundation (6.9 - 1677.104) <7C69F845-F651-3193-8262-5938010EC67D> /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation

0x7fff3123b000 -     0x7fff312dfff3  com.apple.framework.IOKit (2.0.2 - 1726.140.1) <14223387-6F81-3976-8605-4BC2F253A93E> /System/Library/Frameworks/IOKit.framework/Versions/A/IOKit

0x7fff34de8000 -     0x7fff34df4ffe  com.apple.NetFS (6.0 - 4.0) <4415F027-D36D-3B9C-96BA-AD22B44A4722> /System/Library/Frameworks/NetFS.framework/Versions/A/NetFS

0x7fff379d7000 -     0x7fff379f3fff  com.apple.CFOpenDirectory (10.15 - 220.40.1) <7E6C88EB-3DD9-32B0-81FC-179552834FA9> /System/Library/Frameworks/OpenDirectory.framework/Versions/A/Frameworks/CFOpenDirectory.framework/Versions/A/CFOpenDirectory

0x7fff379f4000 -     0x7fff379ffffd  com.apple.OpenDirectory (10.15 - 220.40.1) <4A92D8D8-A9E5-3A9C-942F-28576F6BCDF5> /System/Library/Frameworks/OpenDirectory.framework/Versions/A/OpenDirectory

0x7fff3ad9c000 -     0x7fff3b0e5ff1  com.apple.security (7.0 - 59306.140.5)  /System/Library/Frameworks/Security.framework/Versions/A/Security

0x7fff3b0e6000 -     0x7fff3b16effb  com.apple.securityfoundation (6.0 - 55236.60.1) <7C69DF47-4017-3DF2-B55B-712B481654CB> /System/Library/Frameworks/SecurityFoundation.framework/Versions/A/SecurityFoundation

0x7fff3b19d000 -     0x7fff3b1a1ff8  com.apple.xpc.ServiceManagement (1.0 - 1) <2C62956C-F2D4-3EB0-86C7-EAA06331621A> /System/Library/Frameworks/ServiceManagement.framework/Versions/A/ServiceManagement

0x7fff3be4d000 -     0x7fff3bec7ff7  com.apple.SystemConfiguration (1.19 - 1.19) <84F9B3BB-F7AF-3B7C-8CD0-D3C22D19619F> /System/Library/Frameworks/SystemConfiguration.framework/Versions/A/SystemConfiguration

0x7fff3fe37000 -     0x7fff3fefcfe7  com.apple.APFS (1412.141.1 - 1412.141.1)  /System/Library/PrivateFrameworks/APFS.framework/Versions/A/APFS

0x7fff41c07000 -     0x7fff41c16fd7  com.apple.AppleFSCompression (119.100.1 - 1.0) <466ABD77-2E52-36D1-8E39-77AE2CC61611> /System/Library/PrivateFrameworks/AppleFSCompression.framework/Versions/A/AppleFSCompression

0x7fff433d7000 -     0x7fff433e0ff7  com.apple.coreservices.BackgroundTaskManagement (1.0 - 104)  /System/Library/PrivateFrameworks/BackgroundTaskManagement.framework/Versions/A/BackgroundTaskManagement

0x7fff461e8000 -     0x7fff461f8ff3  com.apple.CoreEmoji (1.0 - 107.1) <7C2B3259-083B-31B8-BCDB-1BA360529936> /System/Library/PrivateFrameworks/CoreEmoji.framework/Versions/A/CoreEmoji

0x7fff46838000 -     0x7fff468a2ff0  com.apple.CoreNLP (1.0 - 213)  /System/Library/PrivateFrameworks/CoreNLP.framework/Versions/A/CoreNLP

0x7fff4771d000 -     0x7fff4774bffd  com.apple.CSStore (1069.24 - 1069.24)  /System/Library/PrivateFrameworks/CoreServicesStore.framework/Versions/A/CoreServicesStore

0x7fff539a9000 -     0x7fff53a77ffd  com.apple.LanguageModeling (1.0 - 215.1)  /System/Library/PrivateFrameworks/LanguageModeling.framework/Versions/A/LanguageModeling

0x7fff53a78000 -     0x7fff53ac0fff  com.apple.Lexicon-framework (1.0 - 72) <41F208B9-8255-3EC7-9673-FE0925D071D3> /System/Library/PrivateFrameworks/Lexicon.framework/Versions/A/Lexicon

0x7fff53ac7000 -     0x7fff53accff3  com.apple.LinguisticData (1.0 - 353.18) <3B92F249-4602-325F-984B-D2DE61EEE4E1> /System/Library/PrivateFrameworks/LinguisticData.framework/Versions/A/LinguisticData

0x7fff54e35000 -     0x7fff54e81fff  com.apple.spotlight.metadata.utilities (1.0 - 2076.7) <0237323B-EC78-3FBF-9FC7-5A1FE2B5CE25> /System/Library/PrivateFrameworks/MetadataUtilities.framework/Versions/A/MetadataUtilities

0x7fff55938000 -     0x7fff55942fff  com.apple.NetAuth (6.2 - 6.2)  /System/Library/PrivateFrameworks/NetAuth.framework/Versions/A/NetAuth

0x7fff5ebce000 -     0x7fff5ebdeff3  com.apple.TCC (1.0 - 1) <017AB27D-6821-303A-8FD2-6DAC795CC7AA> /System/Library/PrivateFrameworks/TCC.framework/Versions/A/TCC

0x7fff622c1000 -     0x7fff622c3ff3  com.apple.loginsupport (1.0 - 1) <12F77885-27DC-3837-9CE9-A25EBA75F833> /System/Library/PrivateFrameworks/login.framework/Versions/A/Frameworks/loginsupport.framework/Versions/A/loginsupport

0x7fff64de1000 -     0x7fff64e15fff  libCRFSuite.dylib (48) <5E5DE3CB-30DD-34DC-AEF8-FE8536A85E96> /usr/lib/libCRFSuite.dylib

0x7fff64e18000 -     0x7fff64e22fff  libChineseTokenizer.dylib (34) <7F0DA183-1796-315A-B44A-2C234C7C50BE> /usr/lib/libChineseTokenizer.dylib

0x7fff64eae000 -     0x7fff64eb0ff7  libDiagnosticMessagesClient.dylib (112)  /usr/lib/libDiagnosticMessagesClient.dylib

0x7fff65384000 -     0x7fff65385fff  libSystem.B.dylib (1281.100.1) <0A6C8BA1-30FD-3D10-83FD-FF29E221AFFE> /usr/lib/libSystem.B.dylib

0x7fff65412000 -     0x7fff65413fff  libThaiTokenizer.dylib (3) <4F4ADE99-0D09-3223-B7C0-C407AB6DE8DC> /usr/lib/libThaiTokenizer.dylib

0x7fff6542b000 -     0x7fff65441fff  libapple_nghttp2.dylib (1.39.2) <07FEC48A-87CF-32A3-8194-FA70B361713A> /usr/lib/libapple_nghttp2.dylib

0x7fff65476000 -     0x7fff654e8ff7  libarchive.2.dylib (72.140.1)  /usr/lib/libarchive.2.dylib

0x7fff65586000 -     0x7fff65586ff3  libauto.dylib (187)  /usr/lib/libauto.dylib

0x7fff6564c000 -     0x7fff6565cffb  libbsm.0.dylib (60.100.1) <00BFFB9A-2FFE-3C24-896A-251BC61917FD> /usr/lib/libbsm.0.dylib

0x7fff6565d000 -     0x7fff65669fff  libbz2.1.0.dylib (44) <14CC4988-B6D4-3879-AFC2-9A0DDC6388DE> /usr/lib/libbz2.1.0.dylib

0x7fff6566a000 -     0x7fff656bcfff  libc++.1.dylib (902.1) <59A8239F-C28A-3B59-B8FA-11340DC85EDC> /usr/lib/libc++.1.dylib

0x7fff656bd000 -     0x7fff656d2ffb  libc++abi.dylib (902)  /usr/lib/libc++abi.dylib

0x7fff656d3000 -     0x7fff656d3fff  libcharset.1.dylib (59) <72447768-9244-39AB-8E79-2FA14EC0AD33> /usr/lib/libcharset.1.dylib

0x7fff656d4000 -     0x7fff656e5fff  libcmph.dylib (8)  /usr/lib/libcmph.dylib

0x7fff656e6000 -     0x7fff656fdfd7  libcompression.dylib (87) <64C91066-586D-38C0-A2F3-3E60A940F859> /usr/lib/libcompression.dylib

0x7fff659d7000 -     0x7fff659edff7  libcoretls.dylib (167) <770A5B96-936E-34E3-B006-B1CEC299B5A5> /usr/lib/libcoretls.dylib

0x7fff659ee000 -     0x7fff659effff  libcoretls_cfhelpers.dylib (167) <940BF370-FD0C-30A8-AA05-FF48DA44FA4C> /usr/lib/libcoretls_cfhelpers.dylib

0x7fff66115000 -     0x7fff66115fff  libenergytrace.dylib (21) <162DFCC0-8F48-3DD0-914F-FA8653E27B26> /usr/lib/libenergytrace.dylib

0x7fff6613c000 -     0x7fff6613efff  libfakelink.dylib (149.1) <36146CB2-E6A5-37BB-9EE8-1B4034D8F3AD> /usr/lib/libfakelink.dylib

0x7fff6614d000 -     0x7fff66152fff  libgermantok.dylib (24)  /usr/lib/libgermantok.dylib

0x7fff6615d000 -     0x7fff6624dfff  libiconv.2.dylib (59) <18311A67-E4EF-3CC7-95B3-C0EDEE3A282F> /usr/lib/libiconv.2.dylib

0x7fff6624e000 -     0x7fff664a5fff  libicucore.A.dylib (64260.0.1) <8AC2CB07-E7E0-340D-A849-186FA1F27251> /usr/lib/libicucore.A.dylib

0x7fff664bf000 -     0x7fff664c0fff  liblangid.dylib (133) <30CFC08C-EF36-3CF5-8AEA-C1CB070306B7> /usr/lib/liblangid.dylib

0x7fff664c1000 -     0x7fff664d9ff3  liblzma.5.dylib (16)  /usr/lib/liblzma.5.dylib

0x7fff664f1000 -     0x7fff66598ff7  libmecab.dylib (883.11) <0D5BFD01-D4A7-3C8D-AA69-C329C1A69792> /usr/lib/libmecab.dylib

0x7fff66599000 -     0x7fff667fbff1  libmecabra.dylib (883.11)  /usr/lib/libmecabra.dylib

0x7fff66cc7000 -     0x7fff67143ff5  libnetwork.dylib (1880.120.4)  /usr/lib/libnetwork.dylib

0x7fff671e4000 -     0x7fff67217fde  libobjc.A.dylib (787.1) <6DF81160-5E7F-3E31-AA1E-C875E3B98AF6> /usr/lib/libobjc.A.dylib

0x7fff6722a000 -     0x7fff6722efff  libpam.2.dylib (25.100.1) <0502F395-8EE6-3D2A-9239-06FD5622E19E> /usr/lib/libpam.2.dylib

0x7fff67231000 -     0x7fff67267ff7  libpcap.A.dylib (89.120.1)  /usr/lib/libpcap.A.dylib

0x7fff6735f000 -     0x7fff67549ff7  libsqlite3.dylib (308.5) <35A2BD9F-4E33-30DE-A994-4AB585AC3AFE> /usr/lib/libsqlite3.dylib

0x7fff6779a000 -     0x7fff6779dffb  libutil.dylib (57)  /usr/lib/libutil.dylib

0x7fff6779e000 -     0x7fff677abff7  libxar.1.dylib (425.2)  /usr/lib/libxar.1.dylib

0x7fff677b1000 -     0x7fff67893fff  libxml2.2.dylib (33.5)  /usr/lib/libxml2.2.dylib

0x7fff67897000 -     0x7fff678bffff  libxslt.1.dylib (16.9) <34A45627-DA5B-37D2-9609-65B425E0010A> /usr/lib/libxslt.1.dylib

0x7fff678c0000 -     0x7fff678d2ff3  libz.1.dylib (76) <793D9643-CD83-3AAC-8B96-88D548FAB620> /usr/lib/libz.1.dylib

0x7fff68181000 -     0x7fff68186ff3  libcache.dylib (83)  /usr/lib/system/libcache.dylib

0x7fff68187000 -     0x7fff68192fff  libcommonCrypto.dylib (60165.120.1)  /usr/lib/system/libcommonCrypto.dylib

0x7fff68193000 -     0x7fff6819afff  libcompiler_rt.dylib (101.2) <49B8F644-5705-3F16-BBE0-6FFF9B17C36E> /usr/lib/system/libcompiler_rt.dylib

0x7fff6819b000 -     0x7fff681a4ff7  libcopyfile.dylib (166.40.1) <3C481225-21E7-370A-A30E-0CCFDD64A92C> /usr/lib/system/libcopyfile.dylib

0x7fff681a5000 -     0x7fff68237fdb  libcorecrypto.dylib (866.140.1) <60567BF8-80FA-359A-B2F3-A3BAEFB288FD> /usr/lib/system/libcorecrypto.dylib

0x7fff68344000 -     0x7fff68384ff0  libdispatch.dylib (1173.100.2)  /usr/lib/system/libdispatch.dylib

0x7fff68385000 -     0x7fff683bbfff  libdyld.dylib (750.6) <789A18C2-8AC7-3C88-813D-CD674376585D> /usr/lib/system/libdyld.dylib

0x7fff683bc000 -     0x7fff683bcffb  libkeymgr.dylib (30)  /usr/lib/system/libkeymgr.dylib

0x7fff683bd000 -     0x7fff683c9ff3  libkxld.dylib (6153.141.2.2) <30AACC57-2314-3863-94B2-64AB3E002B35> /usr/lib/system/libkxld.dylib

0x7fff683ca000 -     0x7fff683caff7  liblaunch.dylib (1738.140.1)  /usr/lib/system/liblaunch.dylib

0x7fff683cb000 -     0x7fff683d0ff7  libmacho.dylib (959.0.1)  /usr/lib/system/libmacho.dylib

0x7fff683d1000 -     0x7fff683d3ff3  libquarantine.dylib (110.40.3)  /usr/lib/system/libquarantine.dylib

0x7fff683d4000 -     0x7fff683d5ff7  libremovefile.dylib (48) <7C7EFC79-BD24-33EF-B073-06AED234593E> /usr/lib/system/libremovefile.dylib

0x7fff683d6000 -     0x7fff683edff3  libsystem_asl.dylib (377.60.2) <1563EE02-0657-3B78-99BE-A947C24122EF> /usr/lib/system/libsystem_asl.dylib

0x7fff683ee000 -     0x7fff683eeff7  libsystem_blocks.dylib (74) <0D53847E-AF5F-3ACF-B51F-A15DEA4DEC58> /usr/lib/system/libsystem_blocks.dylib

0x7fff683ef000 -     0x7fff68476fff  libsystem_c.dylib (1353.100.2)  /usr/lib/system/libsystem_c.dylib

0x7fff68477000 -     0x7fff6847affb  libsystem_configuration.dylib (1061.141.1) <0EE84C33-64FD-372B-974A-AF7A136F2068> /usr/lib/system/libsystem_configuration.dylib

0x7fff6847b000 -     0x7fff6847efff  libsystem_coreservices.dylib (114)  /usr/lib/system/libsystem_coreservices.dylib

0x7fff6847f000 -     0x7fff68487fff  libsystem_darwin.dylib (1353.100.2) <5B12B5DB-3F30-37C1-8ECC-49A66B1F2864> /usr/lib/system/libsystem_darwin.dylib

0x7fff68488000 -     0x7fff6848ffff  libsystem_dnssd.dylib (1096.100.3)  /usr/lib/system/libsystem_dnssd.dylib

0x7fff68490000 -     0x7fff68491ffb  libsystem_featureflags.dylib (17) <29FD922A-EC2C-3F25-BCCC-B58D716E60EC> /usr/lib/system/libsystem_featureflags.dylib

0x7fff68492000 -     0x7fff684dfff7  libsystem_info.dylib (538) <8A321605-5480-330B-AF9E-64E65DE61747> /usr/lib/system/libsystem_info.dylib

0x7fff684e0000 -     0x7fff6850cff7  libsystem_kernel.dylib (6153.141.2.2) <5CDBBC06-6CA6-3432-9FDA-681047866F3E> /usr/lib/system/libsystem_kernel.dylib

0x7fff6850d000 -     0x7fff68554fff  libsystem_m.dylib (3178) <00F331F1-0D09-39B3-8736-1FE90E64E903> /usr/lib/system/libsystem_m.dylib

0x7fff68555000 -     0x7fff6857cfff  libsystem_malloc.dylib (283.100.6) <8549294E-4C53-36EB-99F3-584A7393D8D5> /usr/lib/system/libsystem_malloc.dylib

0x7fff6857d000 -     0x7fff6858affb  libsystem_networkextension.dylib (1095.140.2)  /usr/lib/system/libsystem_networkextension.dylib

0x7fff6858b000 -     0x7fff68594ff7  libsystem_notify.dylib (241.100.2)  /usr/lib/system/libsystem_notify.dylib

0x7fff68595000 -     0x7fff6859dfef  libsystem_platform.dylib (220.100.1) <009A7C1F-313A-318E-B9F2-30F4C06FEA5C> /usr/lib/system/libsystem_platform.dylib

0x7fff6859e000 -     0x7fff685a8fff  libsystem_pthread.dylib (416.100.3) <62CB1A98-0B8F-31E7-A02B-A1139927F61D> /usr/lib/system/libsystem_pthread.dylib

0x7fff685a9000 -     0x7fff685adff3  libsystem_sandbox.dylib (1217.141.2) <051C4018-4345-3034-AC98-6DE42FB8273B> /usr/lib/system/libsystem_sandbox.dylib

0x7fff685ae000 -     0x7fff685b0fff  libsystem_secinit.dylib (62.100.2)  /usr/lib/system/libsystem_secinit.dylib

0x7fff685b1000 -     0x7fff685b8ffb  libsystem_symptoms.dylib (1238.120.1) <5820A2AF-CE72-3AB3-ABCC-273A3419FB55> /usr/lib/system/libsystem_symptoms.dylib

0x7fff685b9000 -     0x7fff685cfff2  libsystem_trace.dylib (1147.120) <04B47629-847B-3D74-8ABE-C05EF9DEEFE4> /usr/lib/system/libsystem_trace.dylib

0x7fff685d1000 -     0x7fff685d6ff7  libunwind.dylib (35.4) <42B7B509-BAFE-365B-893A-72414C92F5BF> /usr/lib/system/libunwind.dylib

0x7fff685d7000 -     0x7fff6860cffe  libxpc.dylib (1738.140.1) <3E243A41-030F-38E3-9FD2-7B38C66C35B1> /usr/lib/system/libxpc.dylib

Sample analysis of process 40325 written to file /dev/stdout

Minimal Reproduction

The code below when compiled with go build and then executed, should immediately hang with 100% processor utilization on a single process thread, when run on a CPU missing either AVX512_BITALG or AVX512_VPOPCNTDQ CPUID feature flags (which I believe at the time of this writing is all Apple Macs Edited to Add: except the top of the line 10th Gen Core (Ice Lake) powered 13" Macbook Pros).

main.go

package main

func popcnt()  // assembly stub

func main() {
	popcnt()
}

popcnt_amd64.s

// +build !gccgo,!purego

#include "textflag.h"

// func popcnt() 
TEXT ·popcnt(SB), NOSPLIT, $0-0

// This instruction causes the Go runtime to immediately hang at 100% CPU utilization
VPOPCNTW Z1, Z0   // Requires AVX512_BITALG

// Or equivalently, so does this one
VPOPCNTQ Z1, Z0  // Requires AVX512_VPOPCNTDQ

RET

[randall77]

Strange.

I get the same behavior from C.

main.c:

void foo();
int main(int argc, char *argv[]) {
  foo();
}

main.s:

	.globl _foo
_foo:
	vpopcntw	%zmm1, %zmm0
	ret

This program also hangs. Compile with gcc main.c main.s, run with ./a.out.
So I think this is an OSX bug, not a Go bug.

Nothing obvious when run under a debugger. The debugger runs it forever, and every time I interrupt it it is at the vpopcntw instruction.

[randall77]

The same C code generates an illegal instruction fault on Linux, so chances are it isn't the chip (although my mac and linux boxes aren't exactly the same chip.)

[vsivsi]

The Darwin kernel has a semi-spooky 2-tier AVX512 thread "promotion" mechanism that involves trapping AVX512 instruction faults, changing thread status to support AVX512, and then rerunning the offending instruction. In theory this scheme should only happen once per process thread upon encountering the first AVX512 instruction. The purpose is to avoid the large additional thread state required for AVX512 (around 2KB) when it is not needed. I would assume that it would only try this promotion procedure once per thread, such that if the AVX512 instruction causing the fault still isn't supported after enabling AVX512 in the thread state, that fault should revert to the process. But I'm way out over my skis on this kind of stuff... Here's the Darwin reference:

https://github.com/apple/darwin-xnu/blob/0a798f6738bc1db01281fc08ae024145e84df927/osfmk/i386/fpu.c#L176

[randall77]

I've submitted a bug to Apple, reference number FB8902463. Their bug reporting tool isn't really public, so I'll report back here if they say anything (which they usually don't, they just silently ignore them).

[vsivsi]

Related to this issue, it appears that on MacOS, the golang.org/x/sys/cpu package does not properly recognize Macs that support AVX512 instructions, due to the Darwin "AVX512 thread promotion" mechanism I mentioned above. Specifically this code incorrectly assumes that OS disabled XSAVE AVX512 thread state can't be changed.

https://github.com/golang/sys/blob/master/cpu/cpu_x86.go#L90

I'm working on a separate issue for this that I'll link here as well.