Crash during GC on arm64

[mkustermann]

From this failure:

/============================================================================\
| standalone_2/no_lazy_dispatchers_test broke (Pass -> Crash, expected Pass) |
\============================================================================/

--- Command "vm" (took 11.000228s):
DART_CONFIGURATION=ReleaseXARM64 out/ReleaseXARM64/dart --no_lazy_dispatchers --ignore-unrecognized-flags --packages=/b/s/w/ir/.packages /b/s/w/ir/tests/standalone_2/no_lazy_dispatchers_test.dart

exit code:
-6

stderr:
===== CRASH =====
si_signo=Segmentation fault(11), si_code=1, si_addr=0xff7974696360
version=2.3.0-edge.13fa51ed541280d916c27e10cb1a47f6831b7135 (Wed May 8 14:49:45 2019 +0000) on "linux_arm64"
thread=13328, isolate=kernel-service(0xaaaaf7197b00)
  pc 0x0000aaaac5251230 fp 0x0000ffff80dfe690 out/ReleaseXARM64/dart+0x18a3230
  pc 0x0000aaaac5258a6c fp 0x0000ffff80dfe6c0 dart::Scavenger::VisitObjectPointers(dart::ObjectPointerVisitor*) const
  pc 0x0000aaaac524fb70 fp 0x0000ffff80dfe770 dart::GCMarker::IterateRoots(dart::ObjectPointerVisitor*)
  pc 0x0000aaaac52513f8 fp 0x0000ffff80dfe800 out/ReleaseXARM64/dart+0x18a33f8
  pc 0x0000aaaac50fbc3c fp 0x0000ffff80dfe840 dart::ThreadPool::Worker::Loop()
  pc 0x0000aaaac50fba6c fp 0x0000ffff80dfe880 dart::ThreadPool::Worker::Main(unsigned long)
  pc 0x0000aaaac5063d00 fp 0x0000ffff80dfe930 out/ReleaseXARM64/dart+0x16b5d00
  pc 0x0000ffff89583fc4 fp 0x0000ffff80dfe940 /lib/aarch64-linux-gnu/libpthread.so.0+0x6fc4
-- End of DumpStackTrace

--- Re-run this test:
python tools/test.py -n dartk-linux-release-arm64 standalone_2/no_lazy_dispatchers_test


/============================================================================\
| vm/dart/generic_field_invocation_test broke (Pass -> Crash, expected Pass) |
\============================================================================/

--- Command "vm" (took 08.000789s):
DART_CONFIGURATION=ReleaseXARM64 out/ReleaseXARM64/dart --no-lazy-dispatchers --ignore-unrecognized-flags --packages=/b/s/w/ir/.packages /b/s/w/ir/runtime/tests/vm/dart/generic_field_invocation_test.dart

exit code:
-6

stderr:
===== CRASH =====
si_signo=Segmentation fault(11), si_code=1, si_addr=0x6c697542646460
version=2.3.0-edge.13fa51ed541280d916c27e10cb1a47f6831b7135 (Wed May 8 14:49:45 2019 +0000) on "linux_arm64"
thread=1764, isolate=kernel-service(0xaaab20a55200)
  pc 0x0000aaaaea548230 fp 0x0000ffff990be6b0 out/ReleaseXARM64/dart+0x18a3230
  pc 0x0000aaaaea54fa6c fp 0x0000ffff990be6e0 dart::Scavenger::VisitObjectPointers(dart::ObjectPointerVisitor*) const
  pc 0x0000aaaaea546b70 fp 0x0000ffff990be790 dart::GCMarker::IterateRoots(dart::ObjectPointerVisitor*)
  pc 0x0000aaaaea547d7c fp 0x0000ffff990be800 out/ReleaseXARM64/dart+0x18a2d7c
  pc 0x0000aaaaea3f2c3c fp 0x0000ffff990be840 dart::ThreadPool::Worker::Loop()
  pc 0x0000aaaaea3f2a6c fp 0x0000ffff990be880 dart::ThreadPool::Worker::Main(unsigned long)
  pc 0x0000aaaaea35ad00 fp 0x0000ffff990be930 out/ReleaseXARM64/dart+0x16b5d00
  pc 0x0000ffff9b49ffc4 fp 0x0000ffff990be940 /lib/aarch64-linux-gnu/libpthread.so.0+0x6fc4
-- End of DumpStackTrace

--- Re-run this test:
python tools/test.py -n dartk-linux-release-arm64 vm/dart/generic_field_invocation_tes

There seem to be cores available for this, see isolate server

/cc @rmacnak-google

[mkustermann]

@mraleph

[alexmarkov]

Still crashing:

 /============================================================================\
 | vm/dart/generic_field_invocation_test broke (Pass -> Crash, expected Pass) |
 \============================================================================/
 --- Command "vm" (took 05.000303s):
 DART_CONFIGURATION=ReleaseXARM64 out/ReleaseXARM64/dart --no-lazy-dispatchers --ignore-unrecognized-flags --packages=/b/s/w/ir/.packages /b/s/w/ir/runtime/tests/vm/dart/generic_field_invocation_test.dart
 exit code:
 -6
 stderr:
 ===== CRASH =====
 si_signo=Segmentation fault(11), si_code=1, si_addr=0x65666552797260
 version=2.8.0-edge.168cf90131a44024f3d6d2c93ce6ac9a17c22f47 (Mon Dec 9 12:51:07 2019 +0000) on "linux_arm64"
 thread=22070, isolate=kernel-service(0xaaaace228400)
   pc 0x0000aaaabb5693fc fp 0x0000ffff8affe6b0 out/ReleaseXARM64/dart+0x1ad73fc
   pc 0x0000aaaabb5716b0 fp 0x0000ffff8affe6e0 dart::Scavenger::VisitObjectPointers(dart::ObjectPointerVisitor*) const
   pc 0x0000aaaabb568184 fp 0x0000ffff8affe790 dart::GCMarker::IterateRoots(dart::ObjectPointerVisitor*)
   pc 0x0000aaaabb56955c fp 0x0000ffff8affe800 out/ReleaseXARM64/dart+0x1ad755c
   pc 0x0000aaaabb415474 fp 0x0000ffff8affe840 dart::ThreadPool::Worker::Loop()
   pc 0x0000aaaabb415278 fp 0x0000ffff8affe870 dart::ThreadPool::Worker::Main(unsigned long)
   pc 0x0000aaaabb395d20 fp 0x0000ffff8affe930 out/ReleaseXARM64/dart+0x1903d20
   pc 0x0000ffff8c6fbfc4 fp 0x0000ffff8affe940 /lib/aarch64-linux-gnu/libpthread.so.0+0x6fc4
 -- End of DumpStackTrace
 --- Re-run this test:
 python tools/test.py -n dartk-linux-release-arm64 vm/dart/generic_field_invocation_test

log

[rmacnak-google]

While iterating new-space, the iteration has gotten confused and thinks the next object starts in the middle of a string object.

                ------------------
0xffff86f802b8:	0x3be08d68004b0304 OneByteString, heapsize=3units, new-bit
         	0x0000000000000026 size=19 code units
0xffff86f802c8:	0x6972745364616572 "readStringReference"
           	0x657265666552676e
0xffff86f802d8:	0x0000ffff8c65636e 
        	0x0000ffff8c280041 (object null)
                ------------------
0xffff86f802e8:	0x20bd6b52004b0204 OneByteString, heapsize=2units, new-bit
              	0x000000000000001c size=14 code units
0xffff86f802f8:	0x6f43676e69727453 "StringConstant"                          <= current
           	0x0000746e6174736e      
                ------------------
0xffff86f80308:	0x00000001004b0204 OneByteString, heapsize=2units, new-bit
         	0x0000000000000000 size=0
0xffff86f80318:	0x0000ffff8c280041 (object null)
           	0x0000ffff8c280041 (object null)
                ------------------

The near-by objects look correct. I'll add some instrumentation to remember the previous object during iteration to try to narrow down how we've gotten here.