Problems persist in KQueueSelectorProvider (Mac) in 7u6 ea (original) (raw)

David Schlosnagle schlosna at gmail.com
Mon Aug 13 14:24:59 PDT 2012

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On Mon, Aug 13, 2012 at 3:13 PM, Jason T. Greene <jason.greene at redhat.com> wrote:

I threw together a quick patch (attached below against 7u-dev), and it appears to resolve the issues on 6 and 7. Although it needs more testing.

The preClose problem disappears as well with this change. My hunch is that the tight spin loop on kqueue makes it impossible for close/dup2 to ever complete.

Hi Jason,

A few minor comments/questions in KQueueArrayWrapper.java:

Should the updateList and Update instance fields all be final? Is there any reason not to avoid the continue in updateRegistrations()? while ((u = updateList.poll()) != null) { SelChImpl ch = u.channel; if (ch.isOpen()) { register0(kq, ch.getFDVal(), u.events & POLLIN, u.events & POLLOUT); } }

Do you foresee any lock contention issues with the synchronization on updateList? Would using a java.util.concurrent.LinkedBlockingQueue rather than the LinkedList with synchronization violate the API semantics of batching the updates? I was thinking something along the lines of the KQueueArrayWrapper.java diff below would work (but I haven't tested at all).

Thanks, Dave

diff --git a/KQueueArrayWrapper.java b/KQueueArrayWrapper.java index 5a7020c..936f086 100644 --- a/KQueueArrayWrapper.java +++ b/KQueueArrayWrapper.java @@ -34,7 +34,9 @@ package sun.nio.ch; import sun.misc.*; import java.io.IOException; import java.io.FileDescriptor;

+import java.util.Iterator; +import java.util.Queue; +import java.util.concurrent.LinkedBlockingQueue;

/*

• struct kevent { // 32-bit 64-bit @@ -85,6 +87,9 @@ class KQueueArrayWrapper { // The fd of the interrupt line coming in private int incomingInterruptFD;

• // The queue of file descriptor registration updates to process
• private final Queue updateQueue = new LinkedBlockingQueue<>();

• static {
      initStructSizes();
      String datamodel = java.security.AccessController.doPrivileged(

@@ -100,6 +105,16 @@ class KQueueArrayWrapper { kq = init(); }

• // Used to update file description registrations
• private static class Update {

•    final SelChImpl channel;

•    final int events;

•    Update(SelChImpl channel, int events) {

•        this.channel = channel;

•        this.events = events;

•    }

• }

• void initInterrupt(int fd0, int fd1) {
      outgoingInterruptFD = fd1;
      incomingInterruptFD = fd0;

@@ -137,12 +152,31 @@ class KQueueArrayWrapper { } }

• void setInterest(int fd, int events) {

•    register0(kq, fd, events & POLLIN, events & POLLOUT);

• void setInterest(SelChImpl channel, int events) {

•    // update existing registration

•    updateQueue.add(new Update(channel, events));

  }

• void release(int fd) {

•    register0(kq, fd, 0, 0);

• void release(SelChImpl channel) {

•    // flush any pending updates

•    for (Iterator<Update> it = updateQueue.iterator(); it.hasNext();) {

•        if (it.next().channel == channel) {

•            it.remove();

•        }

•    }

•    // remove

•    register0(kq, channel.getFDVal(), 0, 0);

• }
• void updateRegistrations() {

•    Update u = null;

•    while ((u = updateQueue.poll()) != null) {

•        SelChImpl ch = u.channel;

•        if (ch.isOpen()) {

•            register0(kq, ch.getFDVal(), u.events & POLLIN,

u.events & POLLOUT);

•        }

•    }

  }

  void close() throws IOException {

@@ -157,6 +191,7 @@ class KQueueArrayWrapper { }

 int poll(long timeout) {

•    updateRegistrations();
     int updated = kevent0(kq, keventArrayAddress, NUM_KEVENTS, timeout);
     return updated;

  }

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