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// Copyright (c) 2011-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif
#include <sync.h>
#include <tinyformat.h>
#include <logging.h>
#include <util/strencodings.h>
#include <util/threadnames.h>
#include <map>
#include <set>
#include <system_error>
#ifdef DEBUG_LOCKCONTENTION
#if !defined(HAVE_THREAD_LOCAL)
static_assert(false, "thread_local is not supported");
#endif
void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
{
LogPrintf("LOCKCONTENTION: %s\n", pszName);
LogPrintf("Locker: %s:%d\n", pszFile, nLine);
}
#endif /* DEBUG_LOCKCONTENTION */
#ifdef DEBUG_LOCKORDER
//
// Early deadlock detection.
// Problem being solved:
// Thread 1 locks A, then B, then C
// Thread 2 locks D, then C, then A
// --> may result in deadlock between the two threads, depending on when they run.
// Solution implemented here:
// Keep track of pairs of locks: (A before B), (A before C), etc.
// Complain if any thread tries to lock in a different order.
//
struct CLockLocation {
CLockLocation(
const char* pszName,
const char* pszFile,
int nLine,
bool fTryIn,
const std::string& thread_name)
: fTry(fTryIn),
mutexName(pszName),
sourceFile(pszFile),
m_thread_name(thread_name),
sourceLine(nLine) {}
std::string ToString() const
{
return strprintf(
"%s %s:%s%s (in thread %s)",
mutexName, sourceFile, sourceLine, (fTry ? " (TRY)" : ""), m_thread_name);
}
std::string Name() const
{
return mutexName;
}
private:
bool fTry;
std::string mutexName;
std::string sourceFile;
const std::string& m_thread_name;
int sourceLine;
};
typedef std::vector<std::pair<void*, CLockLocation> > LockStack;
typedef std::map<std::pair<void*, void*>, LockStack> LockOrders;
typedef std::set<std::pair<void*, void*> > InvLockOrders;
struct LockData {
LockOrders lockorders;
InvLockOrders invlockorders;
std::mutex dd_mutex;
};
LockData& GetLockData() {
// This approach guarantees that the object is not destroyed until after its last use.
// The operating system automatically reclaims all the memory in a program's heap when that program exits.
static LockData& lock_data = *new LockData();
return lock_data;
}
static thread_local LockStack g_lockstack;
static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
{
LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
LogPrintf("Previous lock order was:\n");
for (const std::pair<void*, CLockLocation> & i : s2) {
if (i.first == mismatch.first) {
LogPrintf(" (1)"); /* Continued */
}
if (i.first == mismatch.second) {
LogPrintf(" (2)"); /* Continued */
}
LogPrintf(" %s\n", i.second.ToString());
}
LogPrintf("Current lock order is:\n");
for (const std::pair<void*, CLockLocation> & i : s1) {
if (i.first == mismatch.first) {
LogPrintf(" (1)"); /* Continued */
}
if (i.first == mismatch.second) {
LogPrintf(" (2)"); /* Continued */
}
LogPrintf(" %s\n", i.second.ToString());
}
if (g_debug_lockorder_abort) {
tfm::format(std::cerr, "Assertion failed: detected inconsistent lock order at %s:%i, details in debug log.\n", __FILE__, __LINE__);
abort();
}
throw std::logic_error("potential deadlock detected");
}
static void push_lock(void* c, const CLockLocation& locklocation)
{
LockData& lockdata = GetLockData();
std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
g_lockstack.push_back(std::make_pair(c, locklocation));
for (const std::pair<void*, CLockLocation>& i : g_lockstack) {
if (i.first == c)
break;
std::pair<void*, void*> p1 = std::make_pair(i.first, c);
if (lockdata.lockorders.count(p1))
continue;
lockdata.lockorders.emplace(p1, g_lockstack);
std::pair<void*, void*> p2 = std::make_pair(c, i.first);
lockdata.invlockorders.insert(p2);
if (lockdata.lockorders.count(p2))
potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
}
}
static void pop_lock()
{
g_lockstack.pop_back();
}
void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
{
push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry, util::ThreadGetInternalName()));
}
void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line)
{
if (!g_lockstack.empty()) {
const auto& lastlock = g_lockstack.back();
if (lastlock.first == cs) {
lockname = lastlock.second.Name();
return;
}
}
throw std::system_error(EPERM, std::generic_category(), strprintf("%s:%s %s was not most recent critical section locked", file, line, guardname));
}
void LeaveCritical()
{
pop_lock();
}
std::string LocksHeld()
{
std::string result;
for (const std::pair<void*, CLockLocation>& i : g_lockstack)
result += i.second.ToString() + std::string("\n");
return result;
}
void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
{
for (const std::pair<void*, CLockLocation>& i : g_lockstack)
if (i.first == cs)
return;
tfm::format(std::cerr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld());
abort();
}
void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
{
for (const std::pair<void*, CLockLocation>& i : g_lockstack) {
if (i.first == cs) {
tfm::format(std::cerr, "Assertion failed: lock %s held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld());
abort();
}
}
}
void DeleteLock(void* cs)
{
LockData& lockdata = GetLockData();
std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
std::pair<void*, void*> item = std::make_pair(cs, nullptr);
LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
while (it != lockdata.lockorders.end() && it->first.first == cs) {
std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
lockdata.invlockorders.erase(invitem);
lockdata.lockorders.erase(it++);
}
InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
while (invit != lockdata.invlockorders.end() && invit->first == cs) {
std::pair<void*, void*> invinvitem = std::make_pair(invit->second, invit->first);
lockdata.lockorders.erase(invinvitem);
lockdata.invlockorders.erase(invit++);
}
}
bool g_debug_lockorder_abort = true;
#endif /* DEBUG_LOCKORDER */
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