[jira] Assigned: (HARMONY-3267) [drlvm][thread] Thread.stop() implementation is broken

["weldon washburn (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HARMONY-3267?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

weldon washburn reassigned HARMONY-3267:
----------------------------------------

    Assignee: weldon washburn

> [drlvm][thread] Thread.stop() implementation is broken
> ------------------------------------------------------
>
>                 Key: HARMONY-3267
>                 URL: https://issues.apache.org/jira/browse/HARMONY-3267
>             Project: Harmony
>          Issue Type: Bug
>          Components: DRLVM
>            Reporter: Salikh Zakirov
>         Assigned To: weldon washburn
>            Priority: Minor
>         Attachments: Limited-Thread.stop-fix-for-stopping-waiting-threads.patch, StopBlocked.java, StopBlockedOnMonitor.java, StopWaiting.java
>
>
> The current implementation of Thread.stop() in DRLVM is completely broken.
> The attached tests StopWaiting.java and StopBlocked.java demonstrate current incorrect behaviour:
> DRLVM can't stop the thread which is blocked either waiting or entering monitor.
> The waiting case can be fixed by checking the thread state, setting some checked status and waking thread up, like the patch below.
> However, the blocking case cannot fixed in this way, as we have no easy way to wake up a thread which is blocked on a pthread_mutex_lock or EnterCriticalSection OS call.
> It looks like a correct implementation of stopping blocked thread will require either pthread_kill() or SuspendThread() and modifying thread context (like throwing an exception or longjmp).
> Both tests pass on competition VMs (Sun, Bea, Ibm).
> ----8<-----
> A limited fix for a waiting case only.
> --- vm/thread/src/thread_java_basic.c
> +++ vm/thread/src/thread_java_basic.c
> @@ -416,7 +416,23 @@ void stop_callback(void) {
>      tm_native_thread->suspend_request = 0;
>      hysem_post(tm_native_thread->resume_event);
>      
> +    // Does not return if the exception could be thrown straight away
>      jthread_throw_exception_object(excn);
> +
> +    // getting here means top stack frame is non-unwindable.
> +
> +    if (tm_native_thread->state &
> +            (TM_THREAD_STATE_SLEEPING | TM_THREAD_STATE_WAITING_WITH_TIMEOUT
> +                | TM_THREAD_STATE_WAITING | TM_THREAD_STATE_IN_MONITOR_WAIT
> +                | TM_THREAD_STATE_WAITING_INDEFINITELY | TM_THREAD_STATE_PARKED)) {
> +        // This is needed for correct stopping of a thread blocked on monitor_wait.
> +        // The thread needs some flag to exit its waiting loop.
> +        // We piggy-back on interrupted status. A correct exception from TLS
> +        // will be thrown because the check of exception status on leaving
> +        // JNI frame comes before checking return status in Object.wait().
> +        // Interrupted status will be cleared by 
> +        hythread_interrupt(tm_native_thread);
> +    }
>  }
>  
>  /**

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