Should you capture the return from sleep() to make sure the accumulated timeout of 20 seconds is achieved? Worst case scenario - every sleep is immediately interrupted.
On 8/3/18, 2:37 PM, Gary Adams wrote:
Hello, Please review the following fix for JDK12: http://cr.openjdk.java.net/~cjplummer/8199811/webrev.00 <http://cr.openjdk.java.net/%7Ecjplummer/8199811/webrev.00> https://bugs.openjdk.java.net/browse/JDK-8199811 The root of the problem is that there is no code in the solaris or windows AttachListener support that ensures that the listener is done being initialized before attaching and attempting to enqueue the first command. The enqueue operation fails when is sees that the listener is not attached yet. I was able to force this failure to happen every time by adding a 10 second sleep in attach_listener_thread_entry() just before the call to AttachListener::set_initialized(). This did not cause macosx or linux to fail, but did make solaris fail (failures had not been noted previously) and windows to fail (failures previously had been observed, but very rarely). The proposed fix is to have the enqueue code sleep for up to 20 seconds (in 1 second intervals) waiting for initialization to be complete. I found this fixed the problem, even with the 10 second sleep in attach_listener_thread_entry() still in place. A shorter sleep is probably fine. I'm open to suggestions. Since this timing issue was so rare, my guess is that a single 1 second sleep is likely to always fix it, but since it is so hard to reproduce (without the 10 second sleep in place), I can't say for sure. Another approach to fixing this would be to use some sort of synchronization between the init and enqueue code, like a condition variable. I think I know how to do this with pthread_cond_wait() and pthread_cond_signal(), although it gets to be a bit tricky since I'd probably have to make the enqueue code create the condvar if initialization is not yet complete, and then have the initialization code check for the existence of the condvar when initialization is complete, and signal on it if it exists. I'm pretty sure there's a potential for race condition in there. I haven't thought it through enough to say for sure. I also looked a bit at condition variable support on windows, and it looks like I could do something similar there too. However, I think the sleep approach I have implement is far more straight forward and less error prone, so I'd prefer to stick with it if others approve. thanks, Chris
