internal/trace: TestTraceStress/AllocFree failures

[gopherbot]

#!watchflakes
default <- pkg == "internal/trace" && test == "TestTraceStress/AllocFree"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestTraceStress/AllocFree
    reader_test.go:119: unexpected error while reading the trace: broken trace: failed to advance: frontier:
        [gen=2]
        
        M 87845 [GoUnblock time=235650128960 g=34 g_seq=1 stack=3]
        M 87814 [GoStart time=235650189376 g=34 g_seq=2]
        M 87812 [ProcStart time=235651093760 p=0 p_seq=3]
        M 87780 [ProcStart time=235651125696 p=3 p_seq=14]
        M 87854 [ProcStart time=235651141312 p=3 p_seq=15]
        M 87781 [GoStart time=235654504576 g=19 g_seq=2]
...
        	data="runtime.freeSomeWbufs"
        String id=302
        	data="/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mgcwork.go"
        String id=303
        	data="sync.(*WaitGroup).Add"
        String id=304
        	data="sync.(*WaitGroup).Done"
        EndOfGeneration
        
--- FAIL: TestTraceStress/AllocFree (14.50s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "internal/trace" && test == "TestTraceStress/AllocFree"

2025-10-11 23:12 gotip-linux-amd64-longtest go@1cd71689 internal/trace.TestTraceStress/AllocFree (log)

=== RUN   TestTraceStress/AllocFree
    reader_test.go:119: unexpected error while reading the trace: broken trace: failed to advance: frontier:
        [gen=2]
        
        M 87845 [GoUnblock time=235650128960 g=34 g_seq=1 stack=3]
        M 87814 [GoStart time=235650189376 g=34 g_seq=2]
        M 87812 [ProcStart time=235651093760 p=0 p_seq=3]
        M 87780 [ProcStart time=235651125696 p=3 p_seq=14]
        M 87854 [ProcStart time=235651141312 p=3 p_seq=15]
        M 87781 [GoStart time=235654504576 g=19 g_seq=2]
...
        	data="runtime.freeSomeWbufs"
        String id=302
        	data="/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mgcwork.go"
        String id=303
        	data="sync.(*WaitGroup).Add"
        String id=304
        	data="sync.(*WaitGroup).Done"
        EndOfGeneration
        
--- FAIL: TestTraceStress/AllocFree (14.50s)

— watchflakes