CRASH (net_unittests, others?) dynamorio!common_heap_free from drx soft_kills

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on December 11, 2013 00:52:39_

Our bots all went unstable after updating from r1556 to r1644 . The shift to having soft_kills inside drx is one possible culprit.

The easiest symptom to analyze is a crash that sometimes shows up: http://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Unit%20%28DrMemory%29/builds/14851/steps/memory%20test%3A%20net/logs/stdio [ RUN ] DhcpProxyScriptAdapterFetcher.MockDhcpRealFetch
~~Dr.M~~ WARNING: application is missing line number information.
HTTP server started on 127.0.0.1:49584...
sending server_data: {"host": "127.0.0.1", "port": 49584} (36 bytes)

~~Dr.M~~ Fetching 1 symbol files...
~~Dr.M~~ [1/1] Fetching symbols for C:\Windows\syswow64\msvcrt.dll
~~Dr.M~~ Fetched 1 symbol files successfully
~~Dr.M~~ WARNING: application exited with abnormal code 0xffffffff

command timed out: 1200 seconds without output, attempting to kill
SIGKILL failed to kill process
using fake rc=-1
program finished with exit code -1

remoteFailed: [Failure instance: Traceback from remote host -- Traceback (most recent call last):
Failure: exceptions.RuntimeError: SIGKILL failed to kill process
]

---------------------------

0:000> U dynamorio + 0x6c9feada - 0x6c9b0000
dynamorio!common_heap_free+0xaa [e:\b\build\slave\win-builder\drmemory\dynamorio\core\heap.c @ 3627]:
63b4eada 8b5614 mov edx,[esi+0x14]

% ~/drmemory/git/build_x86_dbg/bin/symquery.exe -e dynamorio/lib32/release/dynamorio.dll -f -a 0x4ef5f
heap_free+0x3f
e:\b\build\slave\win-builder\drmemory\dynamorio\core\heap.c:3710+0xf

% ~/drmemory/git/build_x86_dbg/bin/symquery.exe -e bin/release/drmemorylib.dll -f -a 0x55a41
soft_kills_handle_job_termination+0xb1
e:\b\build\slave\win-builder\drmemory\dynamorio\ext\drx\drx.c:634+0x11

% ~/drmemory/git/build_x86_dbg/bin/symquery.exe -e bin/release/drmemorylib.dll -f -a 0x55c21
soft_kills_pre_syscall+0x191
e:\b\build\slave\win-builder\drmemory\dynamorio\ext\drx\drx.c:745+0xa

% ~/drmemory/git/build_x86_dbg/bin/symquery.exe -e bin/release/drmemorylib.dll -f -a 0x54bed
drmgr_presyscall_event+0x2d
e:\b\build\slave\win-builder\drmemory\dynamorio\ext\drmgr\drmgr.c:982+0xa

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1401_