runtime/pprof: TestLabelSystemstack failure with labeled racecall on linux-amd64-race

[bcmills]

--- FAIL: TestLabelSystemstack (0.22s)
    pprof_test.go:524: total 32 CPU profile samples collected:
        1: 0x40784f (_ZN6__tsan7MetaMap9FreeRangeEPNS_9ProcessorEmm:0) 0x473140 (runtime._System:4621) labels: map[]
        
        1: 0x49c30b (racecall:389) labels: map[key:[value]]
        
        1: 0x407712 (_ZN6__tsan7MetaMap9FreeRangeEPNS_9ProcessorEmm:0) 0x473140 (runtime._System:4621) labels: map[key:[value]]
        
        1: 0x40784f (_ZN6__tsan7MetaMap9FreeRangeEPNS_9ProcessorEmm:0) 0x473140 (runtime._System:4621) labels: map[key:[value]]
        
        3: 0x49d063 (runtime.futex:553) 0x463bb5 (runtime.futexwakeup:68) 0x43dbd2 (runtime.unlock2:120) 0x452ff8 (runtime.unlockWithRank:31 runtime.unlock:111 runtime.setGCPercent.func1:1232) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        2: 0x452f49 (runtime.(*gcControllerState).setGCPercent:1219) 0x452fc4 (runtime.setGCPercent.func1:1229) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        2: 0x43dbbc (runtime.unlock2:115) 0x452ff8 (runtime.unlockWithRank:31 runtime.unlock:111 runtime.setGCPercent.func1:1232) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        5: 0x49d1c7 (runtime.osyield:651) 0x43daab (runtime.lock2:97) 0x452fb1 (runtime.lockWithRank:22 runtime.lock:47 runtime.setGCPercent.func1:1228) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        7: 0x49a746 (runtime.procyield:733) 0x43da72 (runtime.lock2:87) 0x452fb1 (runtime.lockWithRank:22 runtime.lock:47 runtime.setGCPercent.func1:1228) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x43da6e (runtime.lock2:87) 0x452fb1 (runtime.lockWithRank:22 runtime.lock:47 runtime.setGCPercent.func1:1228) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        2: 0x452e8f (runtime.(*gcControllerState).commit:1062) 0x452f55 (runtime.(*gcControllerState).setGCPercent:1219) 0x452fc4 (runtime.setGCPercent.func1:1229) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x43dbe7 (runtime.unlock2:125) 0x452ff8 (runtime.unlockWithRank:31 runtime.unlock:111 runtime.setGCPercent.func1:1232) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x45313e (runtime.gcPaceScavenger:133) 0x452fea (runtime.setGCPercent.func1:1231) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x452d25 (runtime.(*gcControllerState).commit:999) 0x452f55 (runtime.(*gcControllerState).setGCPercent:1219) 0x452fc4 (runtime.setGCPercent.func1:1229) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x452c9e (runtime.(*gcControllerState).commit:970) 0x452f55 (runtime.(*gcControllerState).setGCPercent:1219) 0x452fc4 (runtime.setGCPercent.func1:1229) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x452d7e (runtime.(*gcControllerState).commit:1016) 0x452f55 (runtime.(*gcControllerState).setGCPercent:1219) 0x452fc4 (runtime.setGCPercent.func1:1229) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
        1: 0x49a744 (runtime.procyield:732) 0x43da72 (runtime.lock2:87) 0x452fb1 (runtime.lockWithRank:22 runtime.lock:47 runtime.setGCPercent.func1:1228) 0x498968 (runtime.systemstack:469) 0x495325 (runtime/debug.setGCPercent:1227) 0x5fead9 (runtime/debug.SetGCPercent:92 runtime/pprof.labelHog:1521) 0x5fed92 (runtime/pprof.parallelLabelHog.func1:1534) labels: map[key:[value]]
        
    pprof_test.go:595: runtime.systemstack;key=value: 28
    pprof_test.go:1504: Sample labeled got true want false:  0x49c30b (racecall:389)
FAIL
FAIL	runtime/pprof	8.766s

greplogs --dashboard -md -l -e 'Sample labeled got true want false.*racecall' --since=2021-06-01

2022-01-19T21:14:18-c1296af/linux-amd64-race

(CC @prattmic @felixge; see previously #48577, #50007.)

[bcmills]

Marking as release-blocker for Go 1.18 because this test is new in 1.18.

If I'm reading correctly this failure mode is likely specific to race-detector-enabled builds, so if nothing else it could probably be unblocked by skipping the test under the race detector. (But a fix to the underlying problem would be preferable. 😅)

[prattmic]

I just need to add racecall here. I figured we'd miss a few of these.

[gopherbot]

Change https://golang.org/cl/379834 mentions this issue: runtime/pprof: allow labels on racecall in TestLabelSystemstack