RFR (XS) 8044339: wrong comment for FilterSpuriousWakeups option
lev.priima at oracle.com
Fri May 30 15:57:16 UTC 2014
Thanks for comments, please look at update:
On 05/30/2014 10:03 AM, David Holmes wrote:
> Hi Lev,
> On 30/05/2014 4:33 AM, Lev Priima wrote:
>> Please review and help me with integration:
>> diff -r 102506d9d873 src/share/vm/runtime/globals.hpp
>> --- a/src/share/vm/runtime/globals.hpp Wed May 28 14:42:00 2014 +0400
>> +++ b/src/share/vm/runtime/globals.hpp Thu May 29 22:29:37 2014 +0400
>> @@ -1144,7 +1144,7 @@
>> product(bool, FilterSpuriousWakeups,
>> true, \
>> "Prevent spurious or premature wakeups from object.wait
>> " \
>> - "(Solaris
>> only)") \
>> + "(Ignored for
>> Windows)") \
> Sorry to make life complicated but as I put in the bug report:
> The "Solaris" part dates from the days when Solaris meant "not
> Windows". :)
> A bigger problem here is that the main part of the description:
> "Prevent spurious or premature wakeups from object.wait "
> may not match what people expect - it depends on whether "filter"
> means to remove the item being filtered, or to keep only the item
> being filtered. It would clearer if it read "When true prevents ..."
> but even then it is not accurate as this only excludes spurious
> wakeups from the OS pthread_cond[timed]wait implementation - the JVM
> can still induce its own "spurious wakeups". So the better description
> would be:
> "When true prevents OS-level spurious, or premature, wakeups from
> But it should also be noted that where this flag is checked there is
> an even more inaccurate comment:
> // The underlying Solaris implementation, cond_timedwait, admits
> // spurious/premature wakeups, but the JLS/JVM spec prevents the
> // JVM from making those visible to Java code.
> Ironically this comment appears in the linux and bsd versions but not
> the Solaris one! Further it is incorrect - the JLS/JVMS does not
> prevent spurious wakeups from being made visible to Java code. That
> has always been the intent but it took until Java 5 before we got the
> specification for Object.wait updated to make it clear.
> So really this is all legacy crud that should be removed along with
> the other planned cleanups (ie removing the safe_cond_* functions and
> WorkAroundNPTLTimedWaitHang) and the os_posix refactoring.
> Sorry to mess up your "starter" bug.
>> product(intx, NativeMonitorTimeout, -1,
>> "(Unstable)") \
>> bug: https://bugs.openjdk.java.net/browse/JDK-8044339
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