Issue 1:
Observed a couple of runtime/pprof TestCPUProfileMultithreaded test failures

with the following error message.

--- FAIL: TestCPUProfileMultithreaded (0.26s)
pprof_test.go:169: total 25 CPU profile samples collected
pprof_test.go:185: runtime/pprof_test.cpuHog1: 25
pprof_test.go:185: runtime/pprof_test.cpuHog2: 0
pprof_test.go:199: runtime/pprof_test.cpuHog2 has 0 samples out of 25, want at least 1, ideally 12
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742430 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
invalid spdelta __x86.get_pc_thunk.cx 0xf7742430 0xf7742433 0x0 -1
FAIL
exitcode=1go_android_exec: adb shell rm -rf /data/local/tmp/pprof.test-11065
FAIL runtime/pprof 14.152s

Issue 2:
Weird trybot failure in tsan:

https://storage.googleapis.com/go-build-log/78af9465/linux-amd64-race_91e55cda.log

--- FAIL: TestStackBarrierProfiling (4.60s)
pprof_test.go:342: subprocess failed with signal: segmentation fault:
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5307 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5307 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5307 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a530f 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a530f 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a530f 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5304 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5307 0x0 -1
invalid spdelta _ZN6__tsanL14MemoryRangeSetEPNS_11ThreadStateEmmmy.isra.32.part.33 0x5a5270 0x5a5304 0x0 -1
FAIL
FAIL runtime/pprof 13.799s
2015/12/10 18:38:36 Failed: exit status 1

/cc @aclements