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7035020: ForkJoinPool.invoke may deadlock if parallelism = 1

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Reviewed-by: chegar
This commit is contained in:
Doug Lea 2011-04-08 10:33:14 +01:00
parent 2a48e38d0f
commit e93ee5deba
1 changed files with 17 additions and 15 deletions
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32
jdk/src/share/classes/java/util/concurrent/ForkJoinPool.java
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@ -791,18 +791,19 @@ public class ForkJoinPool extends AbstractExecutorService {
/**
* Tries to enqueue worker w in wait queue and await change in
* worker's eventCount. If the pool is quiescent, possibly
* terminates worker upon exit. Otherwise, before blocking,
* rescans queues to avoid missed signals. Upon finding work,
* releases at least one worker (which may be the current
* worker). Rescans restart upon detected staleness or failure to
* release due to contention. Note the unusual conventions about
* Thread.interrupt here and elsewhere: Because interrupts are
* used solely to alert threads to check termination, which is
* checked here anyway, we clear status (using Thread.interrupted)
* before any call to park, so that park does not immediately
* return due to status being set via some other unrelated call to
* interrupt in user code.
* worker's eventCount. If the pool is quiescent and there is
* more than one worker, possibly terminates worker upon exit.
* Otherwise, before blocking, rescans queues to avoid missed
* signals. Upon finding work, releases at least one worker
* (which may be the current worker). Rescans restart upon
* detected staleness or failure to release due to
* contention. Note the unusual conventions about Thread.interrupt
* here and elsewhere: Because interrupts are used solely to alert
* threads to check termination, which is checked here anyway, we
* clear status (using Thread.interrupted) before any call to
* park, so that park does not immediately return due to status
* being set via some other unrelated call to interrupt in user
* code.
*
* @param w the calling worker
* @param c the ctl value on entry
@ -823,7 +824,7 @@ public class ForkJoinPool extends AbstractExecutorService {
else if (w.eventCount != v)
return true; // update next time
}
if (parallelism + (int)(nc >> AC_SHIFT) == 0 &&
if ((int)c != 0 && parallelism + (int)(nc >> AC_SHIFT) == 0 &&
blockedCount == 0 && quiescerCount == 0)
idleAwaitWork(w, nc, c, v); // quiescent
for (boolean rescanned = false;;) {
@ -893,7 +894,8 @@ public class ForkJoinPool extends AbstractExecutorService {
w.parked = false;
if (w.eventCount != v)
break;
else if (System.nanoTime() - startTime < SHRINK_RATE)
else if (System.nanoTime() - startTime <
SHRINK_RATE - (SHRINK_RATE / 10)) // timing slop
Thread.interrupted(); // spurious wakeup
else if (UNSAFE.compareAndSwapLong(this, ctlOffset,
currentCtl, prevCtl)) {
@ -1175,7 +1177,7 @@ public class ForkJoinPool extends AbstractExecutorService {
ws[k] = w;
nextWorkerIndex = k + 1;
int m = g & SMASK;
g = k >= m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
g = k > m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
}
} finally {
scanGuard = g;