[compiler-rt] r203904 - [sanitizer] partially implement racy fast path in bitset-based deadlock detector
Kostya Serebryany
kcc at google.com
Fri Mar 14 01:06:16 PDT 2014
Author: kcc
Date: Fri Mar 14 03:06:15 2014
New Revision: 203904
URL: http://llvm.org/viewvc/llvm-project?rev=203904&view=rev
Log:
[sanitizer] partially implement racy fast path in bitset-based deadlock detector
Modified:
compiler-rt/trunk/lib/sanitizer_common/sanitizer_bvgraph.h
compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector.h
compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector1.cc
compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_bvgraph_test.cc
Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_bvgraph.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_bvgraph.h?rev=203904&r1=203903&r2=203904&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_bvgraph.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_bvgraph.h Fri Mar 14 03:06:15 2014
@@ -60,6 +60,20 @@ class BVGraph {
return res;
}
+ // *EXPERIMENTAL*
+ // Returns true if all edges from=>to exist.
+ // This function does not use any global state except for 'this' itself,
+ // and thus can be called from different threads w/o locking.
+ // This would be racy.
+ // FIXME: investigate how much we can prove about this race being "benign".
+ bool hasAllEdges(const BV &from, uptr to) {
+ for (typename BV::Iterator it(from); it.hasNext(); ) {
+ uptr idx = it.next();
+ if (!v[idx].getBit(to)) return false;
+ }
+ return true;
+ }
+
// Returns true if the edge from=>to was removed.
bool removeEdge(uptr from, uptr to) {
return v[from].clearBit(to);
Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector.h?rev=203904&r1=203903&r2=203904&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector.h Fri Mar 14 03:06:15 2014
@@ -172,6 +172,16 @@ class DeadlockDetector {
dtls->addLock(cur_idx, current_epoch_);
}
+ // Experimental *racy* fast path function.
+ // Returns true if all edges from the currently held locks to cur_node exist.
+ bool hasAllEdges(DeadlockDetectorTLS<BV> *dtls, uptr cur_node) {
+ if (dtls->getEpoch() == nodeToEpoch(cur_node)) {
+ uptr cur_idx = nodeToIndexUnchecked(cur_node);
+ return g_.hasAllEdges(dtls->getLocks(current_epoch_), cur_idx);
+ }
+ return false;
+ }
+
// Adds edges from currently held locks to cur_node,
// returns the number of added edges, and puts the sources of added edges
// into added_edges[].
Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector1.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector1.cc?rev=203904&r1=203903&r2=203904&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector1.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_deadlock_detector1.cc Fri Mar 14 03:06:15 2014
@@ -100,6 +100,7 @@ void DD::MutexBeforeLock(DDCallback *cb,
DDMutex *m, bool wlock) {
DDLogicalThread *lt = cb->lt;
if (lt->dd.empty()) return; // This will be the first lock held by lt.
+ if (dd.hasAllEdges(<->dd, m->id)) return; // We already have all edges.
SpinMutexLock lk(&mtx);
MutexEnsureID(lt, m);
if (dd.isHeld(<->dd, m->id))
@@ -131,6 +132,7 @@ void DD::MutexAfterLock(DDCallback *cb,
// Printf("T%p MutexLock: %zx\n", lt, m->id);
if (dd.onFirstLock(<->dd, m->id))
return;
+ // if (dd.hasAllEdges(<->dd, m->id)) return;
SpinMutexLock lk(&mtx);
MutexEnsureID(lt, m);
if (wlock) // Only a recursive rlock may be held.
Modified: compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_bvgraph_test.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_bvgraph_test.cc?rev=203904&r1=203903&r2=203904&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_bvgraph_test.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_bvgraph_test.cc Fri Mar 14 03:06:15 2014
@@ -320,10 +320,14 @@ void RunAddEdgesTest() {
from.clear();
from.setBit(1);
EXPECT_EQ(1U, g.addEdges(from, 4, added_edges, kMaxEdges));
+ EXPECT_TRUE(g.hasAllEdges(from, 4));
+ EXPECT_FALSE(g.hasAllEdges(from, 5));
EXPECT_EQ(1U, added_edges[0]);
from.setBit(2);
from.setBit(3);
+ EXPECT_FALSE(g.hasAllEdges(from, 4));
EXPECT_EQ(2U, g.addEdges(from, 4, added_edges, kMaxEdges));
+ EXPECT_TRUE(g.hasAllEdges(from, 4));
EXPECT_EQ(2U, added_edges[0]);
EXPECT_EQ(3U, added_edges[1]);
}
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