On 10/17/06, Nikolay Kuznetsov <[EMAIL PROTECTED]> wrote:
> The simplest model is to grab the thread lock whenever thread A wants to > suspend thread B at a safepoint. While this serializes thread suspension > and can potentially be a bottleneck, let's wait until its a proven > performance problem to change this model. For thread A to be ready to grab > the thread lock, thread A must have all its java live references put in a > place where the GC will see them. Why? Because thread A may block. Once > thread A obtains the lock, it can disable suspension if it likes, reload the > java live refs and do whatever it needs but make certain it is quick and non > blocking. If thread A needs to block on some OS call, etc, it will need to > re-enable suspension and abandon the thread lock. Why? Because if thread A > blocks while holding the global thread lock, there may be deadlock or > latency problems. > > > Did you try the above approach? ARe there deadlocks? I wonder if suspend_disable call can be treated as a thread lock and if yes we do have nearly the same scheme related to stop_the_world suspension.
hmm.... I never thought of it that way. My initial reaction is no. Suspend enable/disable and global thread lock are seperate, distinct concepts. The thread lock should protect the VM internal thread structs when they are being modified. For example, the thread lock should allow only one thread create/die at any given instant. The enable/disable state is incidental to this event. This is independent of the concept of a thread running native code being in a state where the GC can find all its live references. If a thread needs to grab the thread lock, of course, it needs to put itself in a suspend enable mode because it might have to wait for the lock. Nik.
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-- Weldon Washburn Intel Middleware Products Division
