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

[Gerard Ziemski]

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