SF.net SVN: jikesrvm:[15695] rvmroot/trunk/rvm/src/org/jikesrvm/scheduler/ RVMThread.java

Revision: 15695
          http://jikesrvm.svn.sourceforge.net/jikesrvm/?rev=15695&view=rev
Author:   pizlo
Date:     2009-05-25 02:37:12 +0000 (Mon, 25 May 2009)

Log Message:
-----------
Fix hardHandshakeSuspend/Resume so that you can do STW GC while the world is suspended.  Useful for dynamic software updating.  NOTE - this is a tricky change; lets watch the regressions for deadlocks\!

Modified Paths:
--------------
    rvmroot/trunk/rvm/src/org/jikesrvm/scheduler/RVMThread.java

Modified: rvmroot/trunk/rvm/src/org/jikesrvm/scheduler/RVMThread.java
===================================================================
--- rvmroot/trunk/rvm/src/org/jikesrvm/scheduler/RVMThread.java 2009-05-23 02:14:29 UTC (rev 15694)
+++ rvmroot/trunk/rvm/src/org/jikesrvm/scheduler/RVMThread.java 2009-05-25 02:37:12 UTC (rev 15695)
@@ -3214,9 +3214,9 @@
   @Unpreemptible("Does not perform actions that lead to blocking, but may wait for threads to rendezvous with the soft handshake")
   public static void softHandshake(SoftHandshakeVisitor v) {
     handshakeLock.lockWithHandshake(); /*
-                                 * prevent multiple (soft or hard) handshakes
-                                 * from proceeding concurrently
-                                 */
+                                        * prevent multiple (soft or hard) handshakes
+                                        * from proceeding concurrently
+                                        */
 
     int numToHandshake = snapshotHandshakeThreads();
     if (VM.VerifyAssertions)
@@ -3402,12 +3402,15 @@
     RVMThread current=getCurrentThread();
 
     handshakeLock.lockWithHandshake();
+    int numLockedLocks=0;
     for (int i=0;i<nextSlot;++i) {
       Monitor l=communicationLockBySlot[i];
       if (l!=null) {
         l.lockWithHandshake();
+        numLockedLocks++;
       }
     }
+
     // fixpoint until there are no threads that we haven't blocked.
     // fixpoint is needed in case some thread spawns another thread
     // while we're waiting.  that is unlikely but possible.
@@ -3457,6 +3460,17 @@
                                 * that they had stopped.
                                 */
 
+    int numUnlockedLocks=0;
+    for (int i=0;i<nextSlot;++i) {
+      Monitor l=communicationLockBySlot[i];
+      if (l!=null) {
+        l.unlock();
+        numUnlockedLocks++;
+      }
+    }
+    if (VM.VerifyAssertions) VM._assert(numLockedLocks==numUnlockedLocks);
+    handshakeLock.unlock();
+
     if (false) {
       long after=sysCall.sysNanoTime();
       totalSuspendTime+=after-before;
@@ -3470,6 +3484,8 @@
                                          HardHandshakeVisitor hhv) {
     long before=sysCall.sysNanoTime();
 
+    handshakeLock.lockWithHandshake();
+
     RVMThread current=getCurrentThread();
     worldStopped=false;
     acctLock.lockNoHandshake();
@@ -3487,12 +3503,7 @@
       handshakeThreads[i].unblock(ba);
       handshakeThreads[i]=null; // help GC
     }
-    for (int i=0;i<nextSlot;++i) {
-      Monitor l=communicationLockBySlot[i];
-      if (l!=null) {
-        l.unlock();
-      }
-    }
+
     handshakeLock.unlock();
 
     if (false) {
@@ -3502,6 +3513,16 @@
     }
   }
 
+  @Unpreemptible
+  public static void hardHandshakeSuspend() {
+    hardHandshakeSuspend(handshakeBlockAdapter,allButGC);
+  }
+
+  @Unpreemptible
+  public static void hardHandshakeResume() {
+    hardHandshakeResume(handshakeBlockAdapter,allButGC);
+  }
+
   public static boolean worldStopped() {
     return worldStopped;
   }


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