RFR: 8011882: Replace spin loops as back off when suspending

[David Holmes]

Rickard,
On 11/04/2013 9:51 PM, Rickard Bäckman wrote:
> Hi all,
>
> can I please have reviews for this change.
>
> In the current implementation do_suspend uses spin loops to wait until a thread has been suspended. I would like to change that to use semaphores to reduce CPU usage and also make it easier to have a deterministic timeout. Since we are posting to the semaphore in the signal handler we can't use pthread_semaphore since it isn't async safe, which is why all implementations uses low-level os-specific semaphore constructs.

POSIX Semaphore sem_post() is async-signal safe:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04

David
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> Bug: http://bugs.sun.com/view_bug.do?bug_id=8011882
> Webrev: http://cr.openjdk.java.net/~rbackman/8011882/
>
> Thanks
> /R
>