RFR (S): 8149901: [Solaris] Use of -XX:+UseThreadPriorities crashes fastdebug

[David Holmes]

Hi Gerard,

Thanks for looking at this.

On 17/05/2016 1:19 AM, Gerard Ziemski wrote:
> hi David,
>
> The fix seems reasonable, but the following comment seems to be missing the end of its last sentence?
>
> +  // Most thread types will set an explicit priority before starting the thread,
> +  // but for those that don't we need a valid value to read back in thread_native_entry.

This is the complete comment.

> +  // Push a default initial priority into the osThread to be read back when the new

This line is deleted. I forgot to refresh the webrev - now done.

Thanks,
David

> +  osthread->set_native_priority(NormPriority);
> +
>
>
> cheers
>
>> On May 16, 2016, at 12:47 AM, David Holmes <david.holmes at oracle.com> wrote:
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8149901
>>
>> webrev: http://cr.openjdk.java.net/~dholmes/8149901/webrev/
>>
>> JDK-8038473 removed the old code pertaining to use of the T1 threads library and related unused flags - like DefaultThreadPriority. One chunk of code it removed from os::create_thread was:
>>
>> // Set the default thread priority. If using bound threads, setting
>> // lwp priority will be delayed until thread start.
>> set_native_priority(thread, DefaultThreadPriority == -1 ?
>>                              java_to_os_priority[NormPriority] :
>>                              DefaultThreadPriority);
>>
>> but by removing this, the logic in thread_native_entry (formerly java_start) would read back an uninitialized field from the OSThread instance for any thread type (eg VMThread) which did not explicitly set the priority before calling os::start_thread - and that would cause a range check assertion to fire.
>>
>> The simple fix, because we only deal with bound threads (and so we know we will skip most of os::set_native_priority) is to just push a default priority into the OSThread instance directly:
>>
>> osthread->set_native_priority(NormPriority);
>>
>> Ideally I would have fixed this in the OSThread constructor but it is shared code and knows nothing about the native_priority field on Solaris.
>>
>> I found a number of related issues when looking closely at this code, and have filed:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8157010
>>
>> as a followup cleanup for Java 10.
>>
>> Thanks,
>> David
>