Retro68/gcc/libsanitizer/sanitizer_common/sanitizer_deadlock_detector.h
2015-08-28 17:33:40 +02:00

415 lines
14 KiB
C++

//===-- sanitizer_deadlock_detector.h ---------------------------*- C++ -*-===//
//
// 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.
//
// The detector can handle only a fixed amount of simultaneously live locks
// (a lock is alive if it has been locked at least once and has not been
// destroyed). When the maximal number of locks is reached the entire graph
// is flushed and the new lock epoch is started. The node ids from the old
// epochs can not be used with any of the detector methods except for
// nodeBelongsToCurrentEpoch().
//
// 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;
n_recursive_locks = 0;
n_all_locks_ = 0;
}
bool empty() const { return bv_.empty(); }
void ensureCurrentEpoch(uptr current_epoch) {
if (epoch_ == current_epoch) return;
bv_.clear();
epoch_ = current_epoch;
n_recursive_locks = 0;
n_all_locks_ = 0;
}
uptr getEpoch() const { return epoch_; }
// Returns true if this is the first (non-recursive) acquisition of this lock.
bool addLock(uptr lock_id, uptr current_epoch, u32 stk) {
// Printf("addLock: %zx %zx stk %u\n", lock_id, current_epoch, stk);
CHECK_EQ(epoch_, current_epoch);
if (!bv_.setBit(lock_id)) {
// The lock is already held by this thread, it must be recursive.
CHECK_LT(n_recursive_locks, ARRAY_SIZE(recursive_locks));
recursive_locks[n_recursive_locks++] = lock_id;
return false;
}
CHECK_LT(n_all_locks_, ARRAY_SIZE(all_locks_with_contexts_));
// lock_id < BV::kSize, can cast to a smaller int.
u32 lock_id_short = static_cast<u32>(lock_id);
LockWithContext l = {lock_id_short, stk};
all_locks_with_contexts_[n_all_locks_++] = l;
return true;
}
void removeLock(uptr lock_id) {
if (n_recursive_locks) {
for (sptr i = n_recursive_locks - 1; i >= 0; i--) {
if (recursive_locks[i] == lock_id) {
n_recursive_locks--;
Swap(recursive_locks[i], recursive_locks[n_recursive_locks]);
return;
}
}
}
// Printf("remLock: %zx %zx\n", lock_id, epoch_);
if (!bv_.clearBit(lock_id))
return; // probably addLock happened before flush
if (n_all_locks_) {
for (sptr i = n_all_locks_ - 1; i >= 0; i--) {
if (all_locks_with_contexts_[i].lock == static_cast<u32>(lock_id)) {
Swap(all_locks_with_contexts_[i],
all_locks_with_contexts_[n_all_locks_ - 1]);
n_all_locks_--;
break;
}
}
}
}
u32 findLockContext(uptr lock_id) {
for (uptr i = 0; i < n_all_locks_; i++)
if (all_locks_with_contexts_[i].lock == static_cast<u32>(lock_id))
return all_locks_with_contexts_[i].stk;
return 0;
}
const BV &getLocks(uptr current_epoch) const {
CHECK_EQ(epoch_, current_epoch);
return bv_;
}
uptr getNumLocks() const { return n_all_locks_; }
uptr getLock(uptr idx) const { return all_locks_with_contexts_[idx].lock; }
private:
BV bv_;
uptr epoch_;
uptr recursive_locks[64];
uptr n_recursive_locks;
struct LockWithContext {
u32 lock;
u32 stk;
};
LockWithContext all_locks_with_contexts_[64];
uptr n_all_locks_;
};
// 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.
// Most of the methods of this class are not thread-safe (i.e. should
// be protected by an external lock) unless explicitly told otherwise.
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();
n_edges_ = 0;
}
// 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()) {
// Printf("recycling: n_edges_ %zd\n", n_edges_);
for (sptr i = n_edges_ - 1; i >= 0; i--) {
if (recycled_nodes_.getBit(edges_[i].from) ||
recycled_nodes_.getBit(edges_[i].to)) {
Swap(edges_[i], edges_[n_edges_ - 1]);
n_edges_--;
}
}
CHECK(available_nodes_.empty());
// removeEdgesFrom was called in removeNode.
g_.removeEdgesTo(recycled_nodes_);
available_nodes_.setUnion(recycled_nodes_);
recycled_nodes_.clear();
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();
n_edges_ = 0;
return getAvailableNode(data);
}
// Get data associated with the node created by newNode().
uptr getData(uptr node) const { return data_[nodeToIndex(node)]; }
bool nodeBelongsToCurrentEpoch(uptr node) {
return node && (node / size() * size()) == current_epoch_;
}
void removeNode(uptr node) {
uptr idx = nodeToIndex(node);
CHECK(!available_nodes_.getBit(idx));
CHECK(recycled_nodes_.setBit(idx));
g_.removeEdgesFrom(idx);
}
void ensureCurrentEpoch(DeadlockDetectorTLS<BV> *dtls) {
dtls->ensureCurrentEpoch(current_epoch_);
}
// Returns true if there is a cycle in the graph after this lock event.
// Ideally should be called before the lock is acquired so that we can
// report a deadlock before a real deadlock happens.
bool onLockBefore(DeadlockDetectorTLS<BV> *dtls, uptr cur_node) {
ensureCurrentEpoch(dtls);
uptr cur_idx = nodeToIndex(cur_node);
return g_.isReachable(cur_idx, dtls->getLocks(current_epoch_));
}
u32 findLockContext(DeadlockDetectorTLS<BV> *dtls, uptr node) {
return dtls->findLockContext(nodeToIndex(node));
}
// Add cur_node to the set of locks held currently by dtls.
void onLockAfter(DeadlockDetectorTLS<BV> *dtls, uptr cur_node, u32 stk = 0) {
ensureCurrentEpoch(dtls);
uptr cur_idx = nodeToIndex(cur_node);
dtls->addLock(cur_idx, current_epoch_, stk);
}
// 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) {
uptr local_epoch = dtls->getEpoch();
// Read from current_epoch_ is racy.
if (cur_node && local_epoch == current_epoch_ &&
local_epoch == nodeToEpoch(cur_node)) {
uptr cur_idx = nodeToIndexUnchecked(cur_node);
for (uptr i = 0, n = dtls->getNumLocks(); i < n; i++) {
if (!g_.hasEdge(dtls->getLock(i), cur_idx))
return false;
}
return true;
}
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[].
// Should be called before onLockAfter.
uptr addEdges(DeadlockDetectorTLS<BV> *dtls, uptr cur_node, u32 stk,
int unique_tid) {
ensureCurrentEpoch(dtls);
uptr cur_idx = nodeToIndex(cur_node);
uptr added_edges[40];
uptr n_added_edges = g_.addEdges(dtls->getLocks(current_epoch_), cur_idx,
added_edges, ARRAY_SIZE(added_edges));
for (uptr i = 0; i < n_added_edges; i++) {
if (n_edges_ < ARRAY_SIZE(edges_)) {
Edge e = {(u16)added_edges[i], (u16)cur_idx,
dtls->findLockContext(added_edges[i]), stk,
unique_tid};
edges_[n_edges_++] = e;
}
// Printf("Edge%zd: %u %zd=>%zd in T%d\n",
// n_edges_, stk, added_edges[i], cur_idx, unique_tid);
}
return n_added_edges;
}
bool findEdge(uptr from_node, uptr to_node, u32 *stk_from, u32 *stk_to,
int *unique_tid) {
uptr from_idx = nodeToIndex(from_node);
uptr to_idx = nodeToIndex(to_node);
for (uptr i = 0; i < n_edges_; i++) {
if (edges_[i].from == from_idx && edges_[i].to == to_idx) {
*stk_from = edges_[i].stk_from;
*stk_to = edges_[i].stk_to;
*unique_tid = edges_[i].unique_tid;
return true;
}
}
return false;
}
// Test-only function. Handles the before/after lock events,
// returns true if there is a cycle.
bool onLock(DeadlockDetectorTLS<BV> *dtls, uptr cur_node, u32 stk = 0) {
ensureCurrentEpoch(dtls);
bool is_reachable = !isHeld(dtls, cur_node) && onLockBefore(dtls, cur_node);
addEdges(dtls, cur_node, stk, 0);
onLockAfter(dtls, cur_node, stk);
return is_reachable;
}
// Handles the try_lock event, returns false.
// When a try_lock event happens (i.e. a try_lock call succeeds) we need
// to add this lock to the currently held locks, but we should not try to
// change the lock graph or to detect a cycle. We may want to investigate
// whether a more aggressive strategy is possible for try_lock.
bool onTryLock(DeadlockDetectorTLS<BV> *dtls, uptr cur_node, u32 stk = 0) {
ensureCurrentEpoch(dtls);
uptr cur_idx = nodeToIndex(cur_node);
dtls->addLock(cur_idx, current_epoch_, stk);
return false;
}
// Returns true iff dtls is empty (no locks are currently held) and we can
// add the node to the currently held locks w/o chanding the global state.
// This operation is thread-safe as it only touches the dtls.
bool onFirstLock(DeadlockDetectorTLS<BV> *dtls, uptr node, u32 stk = 0) {
if (!dtls->empty()) return false;
if (dtls->getEpoch() && dtls->getEpoch() == nodeToEpoch(node)) {
dtls->addLock(nodeToIndexUnchecked(node), nodeToEpoch(node), stk);
return true;
}
return false;
}
// Finds a path between the lock 'cur_node' (currently not held in dtls)
// and some currently held lock, returns the length of the path
// or 0 on failure.
uptr findPathToLock(DeadlockDetectorTLS<BV> *dtls, uptr cur_node, uptr *path,
uptr path_size) {
tmp_bv_.copyFrom(dtls->getLocks(current_epoch_));
uptr idx = nodeToIndex(cur_node);
CHECK(!tmp_bv_.getBit(idx));
uptr res = g_.findShortestPath(idx, tmp_bv_, path, path_size);
for (uptr i = 0; i < res; i++)
path[i] = indexToNode(path[i]);
if (res)
CHECK_EQ(path[0], cur_node);
return res;
}
// Handle the unlock event.
// This operation is thread-safe as it only touches the dtls.
void onUnlock(DeadlockDetectorTLS<BV> *dtls, uptr node) {
if (dtls->getEpoch() == nodeToEpoch(node))
dtls->removeLock(nodeToIndexUnchecked(node));
}
// Tries to handle the lock event w/o writing to global state.
// Returns true on success.
// This operation is thread-safe as it only touches the dtls
// (modulo racy nature of hasAllEdges).
bool onLockFast(DeadlockDetectorTLS<BV> *dtls, uptr node, u32 stk = 0) {
if (hasAllEdges(dtls, node)) {
dtls->addLock(nodeToIndexUnchecked(node), nodeToEpoch(node), stk);
return true;
}
return false;
}
bool isHeld(DeadlockDetectorTLS<BV> *dtls, uptr node) const {
return dtls->getLocks(current_epoch_).getBit(nodeToIndex(node));
}
uptr testOnlyGetEpoch() const { return current_epoch_; }
bool testOnlyHasEdge(uptr l1, uptr l2) {
return g_.hasEdge(nodeToIndex(l1), nodeToIndex(l2));
}
// idx1 and idx2 are raw indices to g_, not lock IDs.
bool testOnlyHasEdgeRaw(uptr idx1, uptr idx2) {
return g_.hasEdge(idx1, idx2);
}
void Print() {
for (uptr from = 0; from < size(); from++)
for (uptr to = 0; to < size(); to++)
if (g_.hasEdge(from, to))
Printf(" %zx => %zx\n", from, to);
}
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_, nodeToEpoch(node));
}
uptr indexToNode(uptr idx) const {
check_idx(idx);
return idx + current_epoch_;
}
uptr nodeToIndexUnchecked(uptr node) const { return node % size(); }
uptr nodeToIndex(uptr node) const {
check_node(node);
return nodeToIndexUnchecked(node);
}
uptr nodeToEpoch(uptr node) const { return node / size() * size(); }
uptr getAvailableNode(uptr data) {
uptr idx = available_nodes_.getAndClearFirstOne();
data_[idx] = data;
return indexToNode(idx);
}
struct Edge {
u16 from;
u16 to;
u32 stk_from;
u32 stk_to;
int unique_tid;
};
uptr current_epoch_;
BV available_nodes_;
BV recycled_nodes_;
BV tmp_bv_;
BVGraph<BV> g_;
uptr data_[BV::kSize];
Edge edges_[BV::kSize * 32];
uptr n_edges_;
};
} // namespace __sanitizer
#endif // SANITIZER_DEADLOCK_DETECTOR_H