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Rework lock protecting

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When changing 'search' and 'splitPointsSize' we have to
use thread locks, not split point ones, because can_join()
is called under the formers.

Verified succesfully with 24 hours toruture tests with 20
cores machine by Louis Zulli: it does not hangs.

Verifyed for no regressions with STC, 7 threads:
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 52804 W: 8159 L: 8087 D: 36558

No functional change.
This commit is contained in:
Marco Costalba
2015-09-27 14:49:33 +02:00
parent 77b4f4c2e7
commit 3c0fe1d9b2
2 changed files with 12 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
src/thread.cpp
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@@ -145,7 +145,6 @@ void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bes
SplitPoint& sp = splitPoints[splitPointsSize];
sp.spinlock.acquire(); // No contention here until we don't increment splitPointsSize
spinlock.acquire();
sp.master = this;
sp.parentSplitPoint = activeSplitPoint;
@@ -168,7 +167,6 @@ void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bes
++splitPointsSize;
activeSplitPoint = &sp;
activePosition = nullptr;
spinlock.release();
// Try to allocate available threads
Thread* slave;
@@ -196,29 +194,28 @@ void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bes
Thread::idle_loop(); // Force a call to base class idle_loop()
sp.spinlock.acquire();
spinlock.acquire();
// In the helpful master concept, a master can help only a sub-tree of its
// split point and because everything is finished here, it's not possible
// for the master to be booked.
assert(!searching);
assert(!activePosition);
searching = true;
// We have returned from the idle loop, which means that all threads are
// finished. Note that decreasing splitPointsSize must be done under lock
// protection to avoid a race with Thread::can_join().
spinlock.acquire();
searching = true;
--splitPointsSize;
activeSplitPoint = sp.parentSplitPoint;
activePosition = &pos;
spinlock.release();
// Split point data cannot be changed now, so no need to lock protect
pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
*bestMove = sp.bestMove;
*bestValue = sp.bestValue;
spinlock.release();
sp.spinlock.release();
}