Issue 1:
Spotted on the dashboard, from freebsd-386, http://build.golang.org/log/57659ae3bfad2299f82348b400aa9528ad20d8f6

fatal error: unexpected signal during runtime execution
[signal 0xa code=0xc addr=0x2832e000 pc=0x8054f6b]

runtime stack:
runtime.throw(0x8249428, 0x2a)
/tmp/buildlet-scatch781387312/go/src/runtime/panic.go:543 +0x79
runtime.sigpanic()
/tmp/buildlet-scatch781387312/go/src/runtime/sigpanic_unix.go:12 +0x50
runtime.gcmarkwb_m(0x3841459c, 0x583ef960)
/tmp/buildlet-scatch781387312/go/src/runtime/mbarrier.go:73 +0xab
runtime.writebarrierptr_nostore1.func1()
/tmp/buildlet-scatch781387312/go/src/runtime/mbarrier.go:100 +0x111
runtime.systemstack(0x38421f60)
/tmp/buildlet-scatch781387312/go/src/runtime/asm_386.s:283 +0x77
runtime.writebarrierptr_nostore1(0x3841459c, 0x583ef960)
/tmp/buildlet-scatch781387312/go/src/runtime/mbarrier.go:101 +0x50
runtime.writebarrierptr(0x3841459c, 0x583ef960)
/tmp/buildlet-scatch781387312/go/src/runtime/mbarrier.go:124 +0x5b
runtime.acquirep(0x41a8b400)
/tmp/buildlet-scatch781387312/go/src/runtime/proc1.go:2793 +0x6e
runtime.stoplockedm()
/tmp/buildlet-scatch781387312/go/src/runtime/proc1.go:1286 +0x11e
runtime.schedule()
/tmp/buildlet-scatch781387312/go/src/runtime/proc1.go:1577 +0x5d
runtime.goschedImpl(0x383ef080)
/tmp/buildlet-scatch781387312/go/src/runtime/proc1.go:1700 +0xf1
runtime.gosched_m(0x383ef080)
/tmp/buildlet-scatch781387312/go/src/runtime/proc1.go:1708 +0x33
runtime.mcall(0x38421fec)
/tmp/buildlet-scatch781387312/go/src/runtime/asm_386.s:210 +0x43

goroutine 62 [runnable, locked to thread]:
runtime.Gosched()
/tmp/buildlet-scatch781387312/go/src/runtime/proc.go:166 +0x10 fp=0x3840afd0 sp=0x3840afc8
runtime/pprof_test.TestTraceStress.func4(0x41a9d140)
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:141 +0x8f fp=0x3840afe8 sp=0x3840afd0
runtime.goexit()
/tmp/buildlet-scatch781387312/go/src/runtime/asm_386.s:1636 +0x1 fp=0x3840afec sp=0x3840afe8
created by runtime/pprof_test.TestTraceStress
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:144 +0x36f

goroutine 1 [chan receive]:
testing.RunTests(0x8263e28, 0x82fe260, 0xe, 0xe, 0x583ef001)
/tmp/buildlet-scatch781387312/go/src/testing/testing.go:561 +0x875
testing.(*M).Run(0x41ab1f9c, 0x20)
/tmp/buildlet-scatch781387312/go/src/testing/testing.go:490 +0x65
main.main()
runtime/pprof/_test/_testmain.go:82 +0xfd

goroutine 58 [runnable]:
runtime/pprof_test.TestTraceStress(0x38403f20)
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:149 +0x3ad
testing.tRunner(0x38403f20, 0x82fe2e4)
/tmp/buildlet-scatch781387312/go/src/testing/testing.go:452 +0x8c
created by testing.RunTests
/tmp/buildlet-scatch781387312/go/src/testing/testing.go:560 +0x843

goroutine 60 [syscall]:
syscall.Syscall(0x5, 0x3840a7cf, 0x1, 0x1, 0x83024e0, 0x83024e0, 0x80857da)
/tmp/buildlet-scatch781387312/go/src/syscall/asm_freebsd_386.s:20 +0x5
syscall.read(0x5, 0x3840a7cf, 0x1, 0x1, 0x3f064070, 0x0, 0x0)
/tmp/buildlet-scatch781387312/go/src/syscall/zsyscall_freebsd_386.go:890 +0x50
syscall.Read(0x5, 0x3840a7cf, 0x1, 0x1, 0x3844f500, 0x0, 0x0)
/tmp/buildlet-scatch781387312/go/src/syscall/syscall_unix.go:160 +0x46
os.(*File).read(0x38412620, 0x3840a7cf, 0x1, 0x1, 0x3f064070, 0x0, 0x0)
/tmp/buildlet-scatch781387312/go/src/os/file_unix.go:211 +0x6c
os.(*File).Read(0x38412620, 0x3840a7cf, 0x1, 0x1, 0x0, 0x0, 0x0)
/tmp/buildlet-scatch781387312/go/src/os/file.go:95 +0x6c
runtime/pprof_test.TestTraceStress.func3(0x38412620, 0x41a9d140, 0x3846f5c0)
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:120 +0x55
created by runtime/pprof_test.TestTraceStress
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:123 +0x1fb

goroutine 41 [select (no cases)]:
runtime/pprof_test.TestTraceSymbolize.func1()
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:38 +0x18
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:39 +0x174

goroutine 42 [chan send (nil chan)]:
runtime/pprof_test.TestTraceSymbolize.func2()
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:42 +0x38
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:43 +0x189

goroutine 43 [chan receive (nil chan)]:
runtime/pprof_test.TestTraceSymbolize.func3()
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:46 +0x30
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_stack_test.go:47 +0x19e

goroutine 61 [trace reader (blocked)]:
runtime.ReadTrace(0x0, 0x0, 0x0)
/tmp/buildlet-scatch781387312/go/src/runtime/trace.go:318 +0x1bf
runtime/pprof.StartTrace.func1(0x584ff998, 0x38403f80)
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/pprof.go:629 +0x1b
created by runtime/pprof.StartTrace
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/pprof.go:635 +0x6a

goroutine 59 [chan receive]:
runtime/pprof_test.TestTraceStress.func1(0x41a9d140, 0x3846f5c0)
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:104 +0x32
created by runtime/pprof_test.TestTraceStress
/tmp/buildlet-scatch781387312/go/src/runtime/pprof/trace_test.go:106 +0x9d
FAIL runtime/pprof 7.180s

Issue 2:
Not sure this is the same as #9953.

fatal error: unexpected signal during runtime execution
[signal 0xa code=0xc addr=0x28316794 pc=0x80548be]

runtime stack:
runtime.throw(0x82311a8, 0x2a)
/tmp/buildlet-scatch766897833/go/src/runtime/panic.go:543 +0x80
runtime.sigpanic()
/tmp/buildlet-scatch766897833/go/src/runtime/sigpanic_unix.go:12 +0x54
runtime.gcmarkwb_m(0x587a100c, 0x587a1218)
/tmp/buildlet-scatch766897833/go/src/runtime/mbarrier.go:73 +0xae
runtime.writebarrierptr_nostore1.func1()
/tmp/buildlet-scatch766897833/go/src/runtime/mbarrier.go:111 +0x115
runtime.systemstack(0x38409e88)
/tmp/buildlet-scatch766897833/go/src/runtime/asm_386.s:283 +0x77
runtime.writebarrierptr_nostore1(0x587a100c, 0x587a1218)
/tmp/buildlet-scatch766897833/go/src/runtime/mbarrier.go:112 +0x44
runtime.writebarrierptr(0x587a100c, 0x587a1218)
/tmp/buildlet-scatch766897833/go/src/runtime/mbarrier.go:135 +0x7f
runtime.writebarrierslice(0x587a100c, 0x587a1218, 0x689d, 0xfde8)
/tmp/buildlet-scatch766897833/go/src/runtime/mbarrier.go:211 +0x1e
runtime.traceEvent(0x383d6a0e, 0xffffffff, 0x38409f70, 0x1, 0x1)
/tmp/buildlet-scatch766897833/go/src/runtime/trace.go:502 +0x5af
runtime.traceGoStart()
/tmp/buildlet-scatch766897833/go/src/runtime/trace.go:770 +0x81
runtime.execute(0x383d74a0)
/tmp/buildlet-scatch766897833/go/src/runtime/proc1.go:1214 +0xd7
runtime.schedule()
/tmp/buildlet-scatch766897833/go/src/runtime/proc1.go:1418 +0x76
runtime.goschedImpl(0x383d74a0)
/tmp/buildlet-scatch766897833/go/src/runtime/proc1.go:1530 +0xd1
runtime.gosched_m(0x383d74a0)
/tmp/buildlet-scatch766897833/go/src/runtime/proc1.go:1538 +0x33
runtime.mcall(0x383fc52c)
/tmp/buildlet-scatch766897833/go/src/runtime/asm_386.s:210 +0x43

goroutine 66 [running, locked to thread]:
runtime.Gosched()
/tmp/buildlet-scatch766897833/go/src/runtime/proc.go:135 +0x10 fp=0x4c2497d4 sp=0x4c2497cc
runtime/pprof_test.TestTraceStressStartStop.func1.5(0x383e6140)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:269 +0x4a fp=0x4c2497e8 sp=0x4c2497d4
runtime.goexit()
/tmp/buildlet-scatch766897833/go/src/runtime/asm_386.s:2431 +0x1 fp=0x4c2497ec sp=0x4c2497e8
created by runtime/pprof_test.TestTraceStressStartStop.func1
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:272 +0x233

goroutine 1 [chan receive]:
testing.RunTests(0x82528e8, 0x82e7160, 0xe, 0xe, 0x1)
/tmp/buildlet-scatch766897833/go/src/testing/testing.go:561 +0x864
testing.(*M).Run(0x383e8120, 0x82fdac0)
/tmp/buildlet-scatch766897833/go/src/testing/testing.go:490 +0x65
main.main()
/tmp/go-build720119124/runtime/pprof/_test/_testmain.go:82 +0x171

goroutine 89 [semacquire]:
runtime.StopTrace()
/tmp/buildlet-scatch766897833/go/src/runtime/trace.go:184 +0x28
runtime/pprof.StopTrace()
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/pprof.go:642 +0x18
runtime/pprof_test.TestTraceStressStartStop(0x4c23a240)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:356 +0x1c0
testing.tRunner(0x4c23a240, 0x82e71f0)
/tmp/buildlet-scatch766897833/go/src/testing/testing.go:452 +0xa0
created by testing.RunTests
/tmp/buildlet-scatch766897833/go/src/testing/testing.go:560 +0x832

goroutine 40 [select (no cases)]:
runtime/pprof_test.TestTraceSymbolize.func1()
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:38 +0x18
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:39 +0x179

goroutine 41 [chan send (nil chan)]:
runtime/pprof_test.TestTraceSymbolize.func2()
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:42 +0x38
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:43 +0x18e

goroutine 42 [chan receive (nil chan)]:
runtime/pprof_test.TestTraceSymbolize.func3()
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:46 +0x30
created by runtime/pprof_test.TestTraceSymbolize
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_stack_test.go:47 +0x1a3

goroutine 90 [runnable]:
runtime/pprof_test.TestTraceStressStartStop.func1(0x384690c0, 0x4c23a240)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:277 +0x271
created by runtime/pprof_test.TestTraceStressStartStop
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:348 +0x99

goroutine 113 [chan receive]:
runtime/pprof_test.TestTraceStressStartStop.func1.2(0x383e6140, 0x4c23c020)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:241 +0x32
created by runtime/pprof_test.TestTraceStressStartStop.func1
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:243 +0xb7

goroutine 114 [syscall]:
syscall.Syscall(0x3, 0x3ea03fcf, 0x1, 0x1, 0x0, 0x58751218, 0x3128)
/tmp/buildlet-scatch766897833/go/src/syscall/asm_freebsd_386.s:20 +0x5
syscall.read(0x3, 0x3ea03fcf, 0x1, 0x1, 0xb23bb542, 0x0, 0x0)
/tmp/buildlet-scatch766897833/go/src/syscall/zsyscall_freebsd_386.go:890 +0x50
syscall.Read(0x3, 0x3ea03fcf, 0x1, 0x1, 0x58751000, 0x0, 0x0)
/tmp/buildlet-scatch766897833/go/src/syscall/syscall_unix.go:136 +0x46
os.(*File).read(0x4c23e000, 0x3ea03fcf, 0x1, 0x1, 0x9, 0x0, 0x0)
/tmp/buildlet-scatch766897833/go/src/os/file_unix.go:203 +0x6c
os.(*File).Read(0x4c23e000, 0x3ea03fcf, 0x1, 0x1, 0xfde8, 0x0, 0x0)
/tmp/buildlet-scatch766897833/go/src/os/file.go:95 +0x6c
runtime/pprof_test.TestTraceStressStartStop.func1.4(0x4c23e000, 0x383e6140, 0x4c23c020)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:256 +0x54
created by runtime/pprof_test.TestTraceStressStartStop.func1
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:259 +0x202

goroutine 98 [select (no cases)]:
runtime/pprof_test.TestTraceStress.func9()
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:205 +0x1d
created by runtime/pprof_test.TestTraceStress
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/trace_test.go:206 +0x82c

goroutine 67 [trace reader (blocked)]:
runtime.ReadTrace(0x0, 0x0, 0x0)
/tmp/buildlet-scatch766897833/go/src/runtime/trace.go:313 +0x1d2
runtime/pprof.StartTrace.func1(0x584e8918, 0x383eb440)
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/pprof.go:629 +0x1b
created by runtime/pprof.StartTrace
/tmp/buildlet-scatch766897833/go/src/runtime/pprof/pprof.go:635 +0x6a
FAIL runtime/pprof 7.732s