[testbug] compiler/loopstripmining/CheckLoopStripMining.java sets too short a SafepointTimeoutDelay

CompileCommand: compileonly CheckLoopStripMining.test_loop
[5.487s][warning][safepoint]
[5.487s][warning][safepoint] # SafepointSynchronize::begin: Timeout detected:
[5.487s][warning][safepoint] # SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.
[5.487s][warning][safepoint] # SafepointSynchronize::begin: Threads which did not reach the safepoint:
[5.488s][warning][safepoint] # "MainThread" #12 prio=5 os_prio=0 cpu=1750.00ms elapsed=2.77s tid=0x00000038ffd8d800 nid=0x8e3c runnable [0x000000388ef0d000]
[5.488s][warning][safepoint] java.lang.Thread.State: RUNNABLE
[5.488s][warning][safepoint] Thread: 0x00000038ffd8d800 [0x8e3c] State: _running _at_poll_safepoint 1
[5.488s][warning][safepoint] JavaThread state: _thread_blocked
[5.488s][warning][safepoint]
[5.488s][warning][safepoint] # SafepointSynchronize::begin: (End of list)
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=t:/workspace/open/src/hotspot/share/runtime/safepoint.cpp:927
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (t:/workspace/open/src/hotspot/share/runtime/safepoint.cpp:927), pid=11472, tid=45292
# fatal error: Safepoint sync time longer than 500ms detected when executing SafepointALot.
#

The test sets a fixed SafepointTimeoutDelay of 500ms but that may be too short depending on the runtime environment. The thread being waited upon has actually reached the safepoint but we've processed the timeout code before checking again.

We have slow Windows machines where this can crop up.