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preallocate monitor node in monitorWait

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If we don't preallocate the memory we need to reacquire the lock after
we finish waiting, we risk an OOME which may unwind the stack into
code which assumes we still have acquire the lock successfully.
This commit is contained in:
Joel Dice 2011-03-25 18:21:15 -06:00
parent d928d695ff
commit 960bd28296
1 changed files with 14 additions and 6 deletions
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18
src/machine.h
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@ -2794,11 +2794,13 @@ atomicCompareAndSwapObject(Thread* t, object target, unsigned offset,
// Queue Algorithm: http://www.cs.rochester.edu/u/michael/PODC96.html
inline void
monitorAtomicAppendAcquire(Thread* t, object monitor)
monitorAtomicAppendAcquire(Thread* t, object monitor, object node)
{
if (node == 0) {
PROTECT(t, monitor);
object node = makeMonitorNode(t, t, 0);
node = makeMonitorNode(t, t, 0);
}
while (true) {
object tail = monitorAcquireTail(t, monitor);
@ -2878,14 +2880,15 @@ monitorTryAcquire(Thread* t, object monitor)
}
inline void
monitorAcquire(Thread* t, object monitor)
monitorAcquire(Thread* t, object monitor, object node = 0)
{
if (not monitorTryAcquire(t, monitor)) {
PROTECT(t, monitor);
PROTECT(t, node);
ACQUIRE(t, t->lock);
monitorAtomicAppendAcquire(t, monitor);
monitorAtomicAppendAcquire(t, monitor, node);
// note that we don't try to acquire the lock until we're first in
// line, both because it's fair and because we don't support
@ -3009,6 +3012,11 @@ monitorWait(Thread* t, object monitor, int64_t time)
PROTECT(t, monitor);
// pre-allocate monitor node so we don't get an OutOfMemoryError
// when we try to re-acquire the monitor below
object monitorNode = makeMonitorNode(t, t, 0);
PROTECT(t, monitorNode);
{ ACQUIRE(t, t->lock);
monitorAppendWait(t, monitor);
@ -3023,7 +3031,7 @@ monitorWait(Thread* t, object monitor, int64_t time)
interrupted = t->lock->wait(t->systemThread, time);
}
monitorAcquire(t, monitor);
monitorAcquire(t, monitor, monitorNode);
monitorDepth(t, monitor) = depth;