After the fix for 4846970, the same test case hangs as follows (Takes 2-3days):
Two threads (t@11,t@14) encounter simultaneous out_of_bounds exceptions, 1 (t@14) gets the classStructureMonitorEnter lock and proceeds to wait for GC,
the 2nd (t@11) is hung in lwp_mutex_lock with SIGUSR2 disabled,
and so we never successfully suspend for GC.

t@14 (l@15) stopped in ___lwp_cond_wait at 0xef63a484
0xef63a484: ___lwp_cond_wait+0x0004: ta 0x8
        Thread t@14 (0xe8a73dd0) at priority 5
        state: active on l@15
        base function: 0xef2c8fe8: _start() stack: 0xe8a74000[204800]
        flags: NEW_LWP|DETACHED|SUSPENDED
        masked signals: ILL USR1 USR2
        Currently active in ___lwp_cond_wait
current thread: t@14
  [1] ___lwp_cond_wait(0xef52cfa8, 0xef52cf18, 0x0, 0x0, 0x0, 0x0), at 0xef63a484
  [2] __lwp_cond_wait(0xef52cfa8, 0xef52cf18, 0x9c0, 0xef2053f8, 0x6a617661, 0x73756e2f), at 0xef66c548
=>[3] sysCondvarWaitGCOnly(condvar = 0xef52cfa8, mutex = 0xef52cf18), line 86 in "condvar_md.c"
  [4] stable_wait_for_gc_end(self = 0x373088), line 135 in "suspendmutators.c"
  [5] wait_for_gc_end1(self = 0x373088, hasCaptured = TRUE), line 199 in "suspendmutators.c"
  [6] checked_wait_for_gc_end(), line 238 in "suspendmutators.c"
  [7] LLNI_isValidHandleWork(h = 0xf1e54, markOK = FALSE), line 144 in "llni.c"
  [8] LLNI_isValidHandle(h = 0xf1e54), line 151 in "llni.c"
  [9] LLNI_isSameObject(h1 = 0x56f2ac, h2 = 0xf1e54), line 374 in "llni.h"
  [10] CheckSignatureLoaders(signature = 0xebf30 "(JI)V", loader1 = 0x56f2ac, loader2 = 0xf1e54), line 1318 in "loader_ch
eck.c"
  [11] PrepareMethods(cb = 0x56f288), line 852 in "classresolver.c"
  [12] Locked_LinkClass(cb = 0x56f288), line 1660 in "classresolver.c"
  [13] LinkClass(cb = 0x56f288), line 1226 in "classresolver.c"
  [14] Locked_LinkClass(cb = 0x572e90), line 1616 in "classresolver.c"
  [15] LinkClass(cb = 0x572e90), line 1226 in "classresolver.c"
  [16] InitClass(cb = 0x572e90), line 1171 in "classruntime.c"
  [17] FindClassFromClassLoader2(ee = 0x373088, name = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", initialize
= TRUE, loader = 0xef519360, throwError = TRUE, pd = 0xef519360, result = 0xe8a71d20), line 2012 in "classresolver.c"
  [18] FindClassFromClass(ee = 0x373088, name = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", initialize = TRUE,
 from = (nil), result = 0xe8a71d20), line 2051 in "classresolver.c"
  [19] FindErrorClass(cl = 0xe8a71d20, ename = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException"), line 1247 in "clas
sruntime.c"
  [20] SignalError(ename = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", DetailMessage = 0xe8a71e0e "4"), line 1
294 in "classruntime.c"
  [21] JITSignalHandler(sig = 4, info = 0xe8a72510, ucvoid = 0xe8a72258), line 1122 in "compiler_md.c"
  [22] CompiledCodeSignalHandler(sig = 4, info = 0xe8a72510, uc = 0xe8a72258), line 26 in "jit.c"
  [23] panicHandler(sig = 4, siginfo = 0xe8a72510, uc = 0xe8a72258), line 512 in "signals_md.c"
  [24] userSignalHandler(sig = 4, info = 0xe8a72510, uc = 0xe8a72258, arg = 0xef2df680), line 115 in "interrupt.c"
  [25] intrDispatch(interrupt = 4, siginfo = 0xe8a72510, context = 0xe8a72258), line 103 in "interrupt.c"
  [26] intrDispatchMD(sig = 4, info = 0xe8a72510, uc = 0xe8a72258), line 65 in "interrupt_md.c"
  [27] __sighndlr(0x4, 0xe8a72510, 0xe8a72258, 0xef2d5e40, 0xe8a73e48, 0xe8a73e28), at 0xef7165c4
  [28] sigacthandler(0x4, 0xe8a72510, 0xe8a72258, 0xef726b78, 0x10, 0xe8a73e58), at 0xef713a40
  ---- called from signal handler with signal 4 (SIGILL) ------


t@11 (l@11) stopped in ___lwp_mutex_lock at 0xef63a40c
0xef63a40c: ___lwp_mutex_lock+0x0008: ta 0x8
        Thread t@11 (0xee273dd0) at priority 5
        state: active on l@11
        base function: 0xef2c8fe8: _start() stack: 0xee274000[204800]
        flags: NEW_LWP|DETACHED|SUSPENDED
        masked signals: ILL USR1 USR2
        Currently active in ___lwp_mutex_lock
current thread: t@11
  [1] ___lwp_mutex_lock(0x572ee0, 0xef52c5b0, 0x9c4, 0xef2053f8, 0xef726b78, 0xef688c60), at 0xef63a40c
=>[2] sysMutexLock(m = 0x572ee0), line 152 in "mutex_md.c"
  [3] classStructureMonitorEnter(cb = 0x572e90), line 1818 in "monitor.c"
  [4] LinkClass(cb = 0x572e90), line 1225 in "classresolver.c"
  [5] InitClass(cb = 0x572e90), line 1171 in "classruntime.c"
  [6] FindClassFromClassLoader2(ee = 0x3824a8, name = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", initialize =
 TRUE, loader = 0xef519360, throwError = TRUE, pd = 0xef519360, result = 0xee271d20), line 2012 in "classresolver.c"
  [7] FindClassFromClass(ee = 0x3824a8, name = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", initialize = TRUE,
from = (nil), result = 0xee271d20), line 2051 in "classresolver.c"
  [8] FindErrorClass(cl = 0xee271d20, ename = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException"), line 1247 in "class
runtime.c"
  [9] SignalError(ename = 0xef4ec068 "java/lang/ArrayIndexOutOfBoundsException", DetailMessage = 0xee271e0e "4"), line 12
94 in "classruntime.c"
  [10] JITSignalHandler(sig = 4, info = 0xee272510, ucvoid = 0xee272258), line 1122 in "compiler_md.c"
  [11] CompiledCodeSignalHandler(sig = 4, info = 0xee272510, uc = 0xee272258), line 26 in "jit.c"
  [12] panicHandler(sig = 4, siginfo = 0xee272510, uc = 0xee272258), line 512 in "signals_md.c"
  [13] userSignalHandler(sig = 4, info = 0xee272510, uc = 0xee272258, arg = 0xef2df680), line 115 in "interrupt.c"
  [14] intrDispatch(interrupt = 4, siginfo = 0xee272510, context = 0xee272258), line 103 in "interrupt.c"
  [15] intrDispatchMD(sig = 4, info = 0xee272510, uc = 0xee272258), line 65 in "interrupt_md.c"
  [16] __sighndlr(0x4, 0xee272510, 0xee272258, 0xef2d5e40, 0xee273e48, 0xee273e28), at 0xef7165c4
  [17] sigacthandler(0x4, 0xee272510, 0xee272258, 0xef726b78, 0x10, 0xee273e58), at 0xef713a40
  ---- called from signal handler with signal 4 (SIGILL) ------