blob: ccb7065b07aed961e367c0ada403fdc5d927d0fd [file] [log] [blame]
//===-- sanitizer_deadlock_detector1.cpp ----------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Deadlock detector implementation based on NxN adjacency bit matrix.
#include "sanitizer_deadlock_detector_interface.h"
#include "sanitizer_deadlock_detector.h"
#include "sanitizer_allocator_internal.h"
#include "sanitizer_placement_new.h"
#include "sanitizer_mutex.h"
namespace __sanitizer {
typedef TwoLevelBitVector<> DDBV; // DeadlockDetector's bit vector.
struct DDPhysicalThread {
struct DDLogicalThread {
u64 ctx;
DeadlockDetectorTLS<DDBV> dd;
DDReport rep;
bool report_pending;
struct DD final : public DDetector {
SpinMutex mtx;
DeadlockDetector<DDBV> dd;
DDFlags flags;
explicit DD(const DDFlags *flags);
DDPhysicalThread *CreatePhysicalThread() override;
void DestroyPhysicalThread(DDPhysicalThread *pt) override;
DDLogicalThread *CreateLogicalThread(u64 ctx) override;
void DestroyLogicalThread(DDLogicalThread *lt) override;
void MutexInit(DDCallback *cb, DDMutex *m) override;
void MutexBeforeLock(DDCallback *cb, DDMutex *m, bool wlock) override;
void MutexAfterLock(DDCallback *cb, DDMutex *m, bool wlock,
bool trylock) override;
void MutexBeforeUnlock(DDCallback *cb, DDMutex *m, bool wlock) override;
void MutexDestroy(DDCallback *cb, DDMutex *m) override;
DDReport *GetReport(DDCallback *cb) override;
void MutexEnsureID(DDLogicalThread *lt, DDMutex *m);
void ReportDeadlock(DDCallback *cb, DDMutex *m);
DDetector *DDetector::Create(const DDFlags *flags) {
void *mem = MmapOrDie(sizeof(DD), "deadlock detector");
return new(mem) DD(flags);
DD::DD(const DDFlags *flags)
: flags(*flags) {
DDPhysicalThread* DD::CreatePhysicalThread() {
return nullptr;
void DD::DestroyPhysicalThread(DDPhysicalThread *pt) {
DDLogicalThread* DD::CreateLogicalThread(u64 ctx) {
DDLogicalThread *lt = (DDLogicalThread*)InternalAlloc(sizeof(*lt));
lt->ctx = ctx;
lt->report_pending = false;
return lt;
void DD::DestroyLogicalThread(DDLogicalThread *lt) {
void DD::MutexInit(DDCallback *cb, DDMutex *m) {
m->id = 0;
m->stk = cb->Unwind();
void DD::MutexEnsureID(DDLogicalThread *lt, DDMutex *m) {
if (!dd.nodeBelongsToCurrentEpoch(m->id))
m->id = dd.newNode(reinterpret_cast<uptr>(m));
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(&lt->dd, m->id)) return; // We already have all edges.
SpinMutexLock lk(&mtx);
MutexEnsureID(lt, m);
if (dd.isHeld(&lt->dd, m->id))
return; // FIXME: allow this only for recursive locks.
if (dd.onLockBefore(&lt->dd, m->id)) {
// Actually add this edge now so that we have all the stack traces.
dd.addEdges(&lt->dd, m->id, cb->Unwind(), cb->UniqueTid());
ReportDeadlock(cb, m);
void DD::ReportDeadlock(DDCallback *cb, DDMutex *m) {
DDLogicalThread *lt = cb->lt;
uptr path[20];
uptr len = dd.findPathToLock(&lt->dd, m->id, path, ARRAY_SIZE(path));
if (len == 0U) {
// A cycle of 20+ locks? Well, that's a bit odd...
Printf("WARNING: too long mutex cycle found\n");
CHECK_EQ(m->id, path[0]);
lt->report_pending = true;
len = Min<uptr>(len, DDReport::kMaxLoopSize);
DDReport *rep = &lt->rep;
rep->n = len;
for (uptr i = 0; i < len; i++) {
uptr from = path[i];
uptr to = path[(i + 1) % len];
DDMutex *m0 = (DDMutex*)dd.getData(from);
DDMutex *m1 = (DDMutex*)dd.getData(to);
u32 stk_from = 0, stk_to = 0;
int unique_tid = 0;
dd.findEdge(from, to, &stk_from, &stk_to, &unique_tid);
// Printf("Edge: %zd=>%zd: %u/%u T%d\n", from, to, stk_from, stk_to,
// unique_tid);
rep->loop[i].thr_ctx = unique_tid;
rep->loop[i].mtx_ctx0 = m0->ctx;
rep->loop[i].mtx_ctx1 = m1->ctx;
rep->loop[i].stk[0] = stk_to;
rep->loop[i].stk[1] = stk_from;
void DD::MutexAfterLock(DDCallback *cb, DDMutex *m, bool wlock, bool trylock) {
DDLogicalThread *lt = cb->lt;
u32 stk = 0;
if (flags.second_deadlock_stack)
stk = cb->Unwind();
// Printf("T%p MutexLock: %zx stk %u\n", lt, m->id, stk);
if (dd.onFirstLock(&lt->dd, m->id, stk))
if (dd.onLockFast(&lt->dd, m->id, stk))
SpinMutexLock lk(&mtx);
MutexEnsureID(lt, m);
if (wlock) // Only a recursive rlock may be held.
CHECK(!dd.isHeld(&lt->dd, m->id));
if (!trylock)
dd.addEdges(&lt->dd, m->id, stk ? stk : cb->Unwind(), cb->UniqueTid());
dd.onLockAfter(&lt->dd, m->id, stk);
void DD::MutexBeforeUnlock(DDCallback *cb, DDMutex *m, bool wlock) {
// Printf("T%p MutexUnLock: %zx\n", cb->lt, m->id);
dd.onUnlock(&cb->lt->dd, m->id);
void DD::MutexDestroy(DDCallback *cb,
DDMutex *m) {
if (!m->id) return;
SpinMutexLock lk(&mtx);
if (dd.nodeBelongsToCurrentEpoch(m->id))
m->id = 0;
DDReport *DD::GetReport(DDCallback *cb) {
if (!cb->lt->report_pending)
return nullptr;
cb->lt->report_pending = false;
return &cb->lt->rep;
} // namespace __sanitizer