runtime/trace: TestTraceStress{,StartStop} and TestTraceStress fail for go1.5beta2

[GeertJohan]

Compiling go1.5beta2 (cc8f544) fails with the following errors during the tests.

--- FAIL: TestTraceStress (1.67s)
    trace_test.go:226: failed to parse trace: bogus scanning end (offset 892575, time 28614703)
--- FAIL: TestTraceStressStartStop (0.73s)
    trace_test.go:365: failed to parse trace: EvFrequency contains invalid frequency -60703235145 at offset 0x222
--- FAIL: TestTraceFutileWakeup (0.07s)
    trace_test.go:433: failed to parse trace: g 186 is not waiting before unpark (offset 481, time 550)
FAIL
FAIL    runtime/pprof   9.153s

When I ran ./all.bash a second time, it only had a single error:

--- FAIL: TestTraceStressStartStop (0.42s)
    trace_test.go:365: failed to parse trace: bogus scanning end (offset 108133, time 135001278)
FAIL
FAIL    runtime/pprof   9.094s

The third time was different also:

--- FAIL: TestTraceStress (1.55s)
    trace_test.go:226: failed to parse trace: g 5 is not waiting during syscall exit (offset 802828, time 368)
FAIL
FAIL    runtime/pprof   8.248s

go1.4 version: go version go1.4.2 linux/amd64
kernel version: 3.16.0-43-generic #58-Ubuntu SMP
cpu: i7-5820K

There are no other errors during the build.
I'll continue to use go1.5beta2 and update this issue if I bump into trouble, but it looks like it's just runtime/pprof that has a problem. Please let me know when more information or tests are required.

[bradfitz]

Dup of #10512

[GeertJohan]

Whoops, sorry 🍰