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// Copyright (c) 2011-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "sync.h"
#include "util.h"
#include "utilstrencodings.h"
#include <stdio.h>
#include <boost/foreach.hpp>
#include <boost/thread.hpp>
#ifdef DEBUG_LOCKCONTENTION
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)
{
mutexName = pszName;
sourceFile = pszFile;
sourceLine = nLine;
fTry = fTryIn;
}
std::string ToString() const
{
return mutexName + " " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
}
std::string MutexName() const { return mutexName; }
bool fTry;
private:
std::string mutexName;
std::string sourceFile;
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 {
// Very ugly hack: as the global constructs and destructors run single
// threaded, we use this boolean to know whether LockData still exists,
// as DeleteLock can get called by global CCriticalSection destructors
// after LockData disappears.
bool available;
LockData() : available(true) {}
~LockData() { available = false; }
LockOrders lockorders;
InvLockOrders invlockorders;
boost::mutex dd_mutex;
} static lockdata;
boost::thread_specific_ptr<LockStack> lockstack;
static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
{
// We attempt to not assert on probably-not deadlocks by assuming that
// a try lock will immediately have otherwise bailed if it had
// failed to get the lock
// We do this by, for the locks which triggered the potential deadlock,
// in either lockorder, checking that the second of the two which is locked
// is only a TRY_LOCK, ignoring locks if they are reentrant.
bool firstLocked = false;
bool secondLocked = false;
bool onlyMaybeDeadlock = false;
LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
LogPrintf("Previous lock order was:\n");
BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s2) {
if (i.first == mismatch.first) {
LogPrintf(" (1)");
if (!firstLocked && secondLocked && i.second.fTry)
onlyMaybeDeadlock = true;
firstLocked = true;
}
if (i.first == mismatch.second) {
LogPrintf(" (2)");
if (!secondLocked && firstLocked && i.second.fTry)
onlyMaybeDeadlock = true;
secondLocked = true;
}
LogPrintf(" %s\n", i.second.ToString());
}
firstLocked = false;
secondLocked = false;
LogPrintf("Current lock order is:\n");
BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s1) {
if (i.first == mismatch.first) {
LogPrintf(" (1)");
if (!firstLocked && secondLocked && i.second.fTry)
onlyMaybeDeadlock = true;
firstLocked = true;
}
if (i.first == mismatch.second) {
LogPrintf(" (2)");
if (!secondLocked && firstLocked && i.second.fTry)
onlyMaybeDeadlock = true;
secondLocked = true;
}
LogPrintf(" %s\n", i.second.ToString());
}
assert(onlyMaybeDeadlock);
}
static void push_lock(void* c, const CLockLocation& locklocation, bool fTry)
{
if (lockstack.get() == NULL)
lockstack.reset(new LockStack);
boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
(*lockstack).push_back(std::make_pair(c, locklocation));
if (!fTry) {
BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, (*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[p1] = (*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()
{
(*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), fTry);
}
void LeaveCritical()
{
pop_lock();
}
std::string LocksHeld()
{
std::string result;
BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, *lockstack)
result += i.second.ToString() + std::string("\n");
return result;
}
void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
{
BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, *lockstack)
if (i.first == cs)
return;
fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
abort();
}
void DeleteLock(void* cs)
{
if (!lockdata.available) {
// We're already shutting down.
return;
}
boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
std::pair<void*, void*> item = std::make_pair(cs, (void*)0);
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++);
}
}
#endif /* DEBUG_LOCKORDER */
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