mDNSResponder-108.4.tar.gz

[apple/mdnsresponder.git] / mDNSShared / Java / DNSSD.java

diff --git a/mDNSShared/Java/DNSSD.java b/mDNSShared/Java/DNSSD.java
index d8a7ce1aba660215aef13e99c99cb2a7ce414b4c..50d29e411e7e2722ef69255afa867780652ffe4d 100644 (file)
--- a/mDNSShared/Java/DNSSD.java
+++ b/mDNSShared/Java/DNSSD.java
@@ -23,6 +23,9 @@
     Change History (most recent first):
 
 $Log: DNSSD.java,v $
+Revision 1.9  2005/10/26 01:52:24  cheshire
+<rdar://problem/4316286> Race condition in Java code (doesn't work at all on Linux)
+
 Revision 1.8  2005/07/11 01:55:21  cheshire
 <rdar://problem/4175511> Race condition in Java API
 
@@ -652,8 +655,8 @@ class       AppleService implements DNSSDService, Runnable
 
        public void                             stop() { this.HaltOperation(); }
 
-       /* Block for timeout ms (or forever if -1). Returns 1 if data present, 0 if timed out, -1 if not browsing. */
-       protected native int    BlockForData( int msTimeout);
+       /* Block until data arrives, or one second passes. Returns 1 if data present, 0 otherwise. */
+       protected native int    BlockForData();
 
        /* Call ProcessResults when data appears on socket descriptor. */
        protected native int    ProcessResults();
@@ -672,7 +675,9 @@ class       AppleService implements DNSSDService, Runnable
        {
                while ( true )
                {
-                       // We have to be very careful here. Suppose our DNS-SD operation is stopped from some other thread,
+                       // Note: We want to allow our DNS-SD operation to be stopped from other threads, so we have to
+                       // block waiting for data *outside* the synchronized section. Because we're doing this unsynchronized
+                       // we have to write some careful code. Suppose our DNS-SD operation is stopped from some other thread,
                        // and then immediately afterwards that thread (or some third, unrelated thread) starts a new DNS-SD
                        // operation. The Unix kernel always allocates the lowest available file descriptor to a new socket,
                        // so the same file descriptor is highly likely to be reused for the new operation, and if our old
@@ -691,11 +696,11 @@ class     AppleService implements DNSSDService, Runnable
                        // locking DOESN'T prevent the callback routine from stopping its own operation, but DOES prevent
                        // any other thread from stopping it until after the callback has completed and returned to us here.
 
-                       int result = BlockForData(-1);
-                       if (result != 1) break; // If socket has been closed, time to terminate this thread
+                       int result = BlockForData();
                        synchronized (this)
                        {
                                if (fNativeContext == 0) break; // Some other thread stopped our DNSSD operation; time to terminate this thread
+                               if (result == 0) continue;              // If BlockForData() said there was no data, go back and block again
                                result = ProcessResults();
                                if (fNativeContext == 0) break; // Event listener stopped its own DNSSD operation; terminate this thread
                                if (result != 0) { fListener.operationFailed(this, result); break; }    // If error, notify listener