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diff --git a/src/sync.cpp b/src/sync.cpp
index a422939964..1837e8d53d 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -1,147 +1,176 @@
// Copyright (c) 2011-2012 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)
+ 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);
+ 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;
static boost::mutex dd_mutex;
static std::map<std::pair<void*, void*>, LockStack> lockorders;
static 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)
+ if (i.first == mismatch.first) {
LogPrintf(" (1)");
- if (i.first == mismatch.second)
+ 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)
+ if (i.first == mismatch.first) {
LogPrintf(" (1)");
- if (i.first == mismatch.second)
+ 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);
dd_mutex.lock();
(*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 (lockorders.count(p1))
continue;
lockorders[p1] = (*lockstack);
std::pair<void*, void*> p2 = std::make_pair(c, i.first);
- if (lockorders.count(p2)) {
+ if (lockorders.count(p2))
potential_deadlock_detected(p1, lockorders[p2], lockorders[p1]);
- break;
- }
}
}
dd_mutex.unlock();
}
static void pop_lock()
{
dd_mutex.lock();
(*lockstack).pop_back();
dd_mutex.unlock();
}
void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
{
- push_lock(cs, CLockLocation(pszName, pszFile, nLine), 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();
}
#endif /* DEBUG_LOCKORDER */

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