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//===-- sanitizer_deadlock_detector.h ---------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of Sanitizer runtime.
// The deadlock detector maintains a directed graph of lock acquisitions.
// When a lock event happens, the detector checks if the locks already held by
// the current thread are reachable from the newly acquired lock.
//
// FIXME: this is work in progress, nothing really works yet.
//
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_DEADLOCK_DETECTOR_H
#define SANITIZER_DEADLOCK_DETECTOR_H
#include "sanitizer_common.h"
#include "sanitizer_bvgraph.h"
namespace __sanitizer {
// Thread-local state for DeadlockDetector.
// It contains the locks currently held by the owning thread.
template <class BV>
class DeadlockDetectorTLS {
public:
// No CTOR.
void clear() {
bv_.clear();
epoch_ = 0;
}
void addLock(uptr lock_id, uptr current_epoch) {
if (current_epoch != epoch_) {
bv_.clear();
epoch_ = current_epoch;
}
bv_.setBit(lock_id);
}
void removeLock(uptr lock_id, uptr current_epoch) {
if (current_epoch != epoch_) {
bv_.clear();
epoch_ = current_epoch;
}
bv_.clearBit(lock_id);
}
const BV &getLocks() const { return bv_; }
private:
BV bv_;
uptr epoch_;
};
// DeadlockDetector.
// For deadlock detection to work we need one global DeadlockDetector object
// and one DeadlockDetectorTLS object per evey thread.
// This class is not thread safe, all concurrent accesses should be guarded
// by an external lock.
// Not thread-safe, all accesses should be protected by an external lock.
template <class BV>
class DeadlockDetector {
public:
typedef BV BitVector;
uptr size() const { return g_.size(); }
// No CTOR.
void clear() {
current_epoch_ = 0;
available_nodes_.clear();
recycled_nodes_.clear();
g_.clear();
}
// Allocate new deadlock detector node.
// If we are out of available nodes first try to recycle some.
// If there is nothing to recycle, flush the graph and increment the epoch.
// Associate 'data' (opaque user's object) with the new node.
uptr newNode(uptr data) {
if (!available_nodes_.empty())
return getAvailableNode(data);
if (!recycled_nodes_.empty()) {
CHECK(available_nodes_.empty());
available_nodes_.setUnion(recycled_nodes_);
recycled_nodes_.clear();
// FIXME: actually recycle nodes in the graph.
return getAvailableNode(data);
}
// We are out of vacant nodes. Flush and increment the current_epoch_.
current_epoch_ += size();
recycled_nodes_.clear();
available_nodes_.setAll();
g_.clear();
return getAvailableNode(data);
}
// Get data associated with the node created by newNode().
uptr getData(uptr node) const { return data_[nodeToIndex(node)]; }
void removeNode(uptr node) {
uptr idx = nodeToIndex(node);
CHECK(!available_nodes_.getBit(idx));
CHECK(recycled_nodes_.setBit(idx));
// FIXME: also remove from the graph.
}
// Handle the lock event, return true if there is a cycle.
// FIXME: handle RW locks, recusive locks, etc.
bool onLock(DeadlockDetectorTLS<BV> *dtls, uptr cur_node) {
uptr cur_idx = nodeToIndex(cur_node);
bool is_reachable = g_.isReachable(cur_idx, dtls->getLocks());
dtls->addLock(cur_idx, current_epoch_);
g_.addEdges(dtls->getLocks(), cur_idx);
return is_reachable;
}
// Handle the unlock event.
void onUnlock(DeadlockDetectorTLS<BV> *dtls, uptr node) {
dtls->removeLock(nodeToIndex(node), current_epoch_);
}
private:
void check_idx(uptr idx) const { CHECK_LT(idx, size()); }
void check_node(uptr node) const {
CHECK_GE(node, size());
CHECK_EQ(current_epoch_, node / size() * size());
}
uptr indexToNode(uptr idx) const {
check_idx(idx);
return idx + current_epoch_;
}
uptr nodeToIndex(uptr node) const {
check_node(node);
return node % size();
}
uptr getAvailableNode(uptr data) {
uptr idx = available_nodes_.getAndClearFirstOne();
data_[idx] = data;
return indexToNode(idx);
}
uptr current_epoch_;
BV available_nodes_;
BV recycled_nodes_;
BVGraph<BV> g_;
uptr data_[BV::kSize];
};
} // namespace __sanitizer
#endif // SANITIZER_DEADLOCK_DETECTOR_H
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