Race in dbus

[purpleidea]

I seem to be able to trigger this fairly reliably. It pops up in two different ways, both are listed here.

I will admit that the code I wrote which uses this is very old and ugly, but a cursory look leads me to believe it's likely a bug in this library.

If you'd like more information, please let me know. FIgured I'd post this in case it's an obvious fix for the maintainers.

I'm happy to share code to reproduce it, but it's quite involved because https://github.com/purpleidea/mgmt/ which consumes this is not exactly small, so hopefully the trace is helpful.

Thanks!

==================
WARNING: DATA RACE
Read at 0x00c00235dc50 by goroutine 645:
  runtime.mapaccess2_faststr()
      /usr/lib/golang/src/internal/runtime/maps/runtime_faststr_swiss.go:162 +0x0
  github.com/coreos/go-systemd/v22/dbus.(*set).Contains()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/set.go:30 +0x68
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).filter()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:29 +0x2b
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).Subscribe.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:38 +0xe
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:119 +0x318
  github.com/coreos/go-systemd/v22/dbus.(*Conn).ListUnits()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/methods.go:452 +0xd3
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:115 +0x9f

Previous write at 0x00c00235dc50 by goroutine 421:
  runtime.mapassign_faststr()
      /usr/lib/golang/src/internal/runtime/maps/runtime_faststr_swiss.go:263 +0x0
  github.com/coreos/go-systemd/v22/dbus.(*set).Add()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/set.go:22 +0xc7b
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:242 +0xc31
  github.com/coreos/go-systemd/v22/dbus.(*Conn).GetUnitPropertyContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/methods.go:333 +0x93c
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:204 +0x8ef
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:175 +0x2e2
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:101 +0x9e7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:97 +0x9d1
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/purpleidea/mgmt/util.SystemBusPrivateUsable()
      /home/james/code/mgmt/util/util.go:632 +0x44
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:167 +0x1a7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:196 +0x5a
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:191 +0x3b
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:138 +0x72
  github.com/coreos/go-systemd/v22/dbus.NewWithContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:123 +0x34
  github.com/coreos/go-systemd/v22/dbus.New()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:117 +0xd3
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:156 +0xb7
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker.func1()
      /home/james/code/mgmt/engine/graph/actions.go:521 +0x7da

Goroutine 645 (running) created at:
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:111 +0x27c
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).Subscribe()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:36 +0xb1
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:191 +0x88a
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:175 +0x2e2
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:101 +0x9e7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:97 +0x9d1
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/purpleidea/mgmt/util.SystemBusPrivateUsable()
      /home/james/code/mgmt/util/util.go:632 +0x44
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:167 +0x1a7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:196 +0x5a
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:191 +0x3b
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:138 +0x72
  github.com/coreos/go-systemd/v22/dbus.NewWithContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:123 +0x34
  github.com/coreos/go-systemd/v22/dbus.New()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:117 +0xd3
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:156 +0xb7
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker.func1()
      /home/james/code/mgmt/engine/graph/actions.go:521 +0x7da

Goroutine 421 (running) created at:
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker()
      /home/james/code/mgmt/engine/graph/actions.go:450 +0xa24
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Commit.func1.2.1()
      /home/james/code/mgmt/engine/graph/engine.go:310 +0x2ba
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Commit.func1.2.gowrap1()
      /home/james/code/mgmt/engine/graph/engine.go:325 +0x4f
==================


==================
WARNING: DATA RACE
Read at 0x00c000af8288 by goroutine 645:
  github.com/coreos/go-systemd/v22/dbus.(*set).Contains()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/set.go:30 +0x71
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).filter()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:29 +0x2b
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).Subscribe.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:38 +0xe
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:119 +0x318
  github.com/coreos/go-systemd/v22/dbus.(*Conn).ListUnits()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/methods.go:452 +0xd3
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:115 +0x9f

Previous write at 0x00c000af8288 by goroutine 421:
  github.com/coreos/go-systemd/v22/dbus.(*set).Add()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/set.go:22 +0xc8a
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:242 +0xc31
  github.com/coreos/go-systemd/v22/dbus.(*Conn).GetUnitPropertyContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/methods.go:333 +0x93c
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:204 +0x8ef
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:175 +0x2e2
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:101 +0x9e7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:97 +0x9d1
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/purpleidea/mgmt/util.SystemBusPrivateUsable()
      /home/james/code/mgmt/util/util.go:632 +0x44
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:167 +0x1a7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:196 +0x5a
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:191 +0x3b
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:138 +0x72
  github.com/coreos/go-systemd/v22/dbus.NewWithContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:123 +0x34
  github.com/coreos/go-systemd/v22/dbus.New()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:117 +0xd3
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:156 +0xb7
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker.func1()
      /home/james/code/mgmt/engine/graph/actions.go:521 +0x7da

Goroutine 645 (running) created at:
  github.com/coreos/go-systemd/v22/dbus.(*Conn).SubscribeUnitsCustom()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription.go:111 +0x27c
  github.com/coreos/go-systemd/v22/dbus.(*SubscriptionSet).Subscribe()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/subscription_set.go:36 +0xb1
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:191 +0x88a
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:175 +0x2e2
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:101 +0x9e7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:97 +0x9d1
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/purpleidea/mgmt/util.SystemBusPrivateUsable()
      /home/james/code/mgmt/util/util.go:632 +0x44
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:167 +0x1a7
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:196 +0x5a
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:200 +0xb5c
  github.com/godbus/dbus/v5.(*Conn).tryAuth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:133 +0x67
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:86 +0x919
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:80 +0x8ad
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:68 +0x47c
  github.com/godbus/dbus/v5.(*Conn).Auth()
      /home/james/code/gopath/pkg/mod/github.com/godbus/dbus/v5@v5.1.0/auth.go:64 +0x466
  github.com/coreos/go-systemd/v22/dbus.dbusAuthConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:242 +0x1b6
  github.com/coreos/go-systemd/v22/dbus.dbusAuthHelloConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:252 +0x3e
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext.func1()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:139 +0x44
  github.com/coreos/go-systemd/v22/dbus.NewConnection()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:191 +0x3b
  github.com/coreos/go-systemd/v22/dbus.NewSystemConnectionContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:138 +0x72
  github.com/coreos/go-systemd/v22/dbus.NewWithContext()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:123 +0x34
  github.com/coreos/go-systemd/v22/dbus.New()
      /home/james/code/gopath/pkg/mod/github.com/coreos/go-systemd/v22@v22.6.0/dbus/dbus.go:117 +0xd3
  github.com/purpleidea/mgmt/engine/resources.(*SvcRes).Watch()
      /home/james/code/mgmt/engine/resources/svc.go:156 +0xb7
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker.func1()
      /home/james/code/mgmt/engine/graph/actions.go:521 +0x7da

Goroutine 421 (running) created at:
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Worker()
      /home/james/code/mgmt/engine/graph/actions.go:450 +0xa24
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Commit.func1.2.1()
      /home/james/code/mgmt/engine/graph/engine.go:310 +0x2ba
  github.com/purpleidea/mgmt/engine/graph.(*Engine).Commit.func1.2.gowrap1()
      /home/james/code/mgmt/engine/graph/engine.go:325 +0x4f
==================

[Luap99]

Are you modifying the SubscriptionSet after you called Subscribe() on it?

Subscribe() spawns a gorouting which will read from the set (map) so adding new things afterwards is no longer safe.
It should be possible to add a mutex to the map to prevent concurrent access here in theory if modifying it is a valid use case.

What I find worse however is that Subscribe() calls SubscribeUnitsCustom() which spawns the goroutine with no way to cancel it. So I am not sure this is a particular a sane API I would recommend to be used.
cc @kolyshkin

[purpleidea]

Are you modifying the SubscriptionSet after you called Subscribe() on it?

Indeed I am.

Now to be perfectly fair, as I mentioned, this is in some old ugly code, which is assuredly not optimal, but at the bare minimum this should be either documented as being not thread safe, or fixed I think.

If you believe this is crazy behaviour on my part to even hit this, then I will accept that as an answer, and look into rewriting my code before I persist here.

Anything else you need, please let me know. Thank you!

[purpleidea]

I'm having a deeper look at this. AFAICT (If I'm groking the API properly) this is confirmed from my POV as a bug...

I imagine the way I envisioned this is that you build a subscription set, and periodically you change what you're interested in... So I'd expect it to be thread safe and dynamically adjusting to what we're requesting.

Otherwise I assume you'd have to do some weird hacky stuff where you start a new subscription, and only after you know it's ready (how???) do you then kill off the other one?

HTH

[Luap99]

only after you know it's ready (how???) do you then kill off the other one?

Like I mentioned there is no way, each Subscribe() leaks one goroutine.

so yeah sure adding a mutex here does make sense if there are users who have to update the set, PRs welcome.

But really the fact that this cannot be cancelled using a context is just a broken API. At the very least the function comments must be updated to warn of this issue. Or better we deprecate that function and add a SubscribeContext alternative which can be cancelled.