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/**
*
* @file DeadlockRule.cpp
* @author Gaspard Kirira
*
* Copyright 2025, Gaspard Kirira. All rights reserved.
* https://github.com/vixcpp/vix
* Use of this source code is governed by a MIT license
* that can be found in the License file.
*
* Vix.cpp
*
*/
#include <vix/cli/errors/runtime/IRuntimeErrorRule.hpp>
#include <vix/cli/errors/runtime/RuntimeRuleUtils.hpp>
#include <cctype>
#include <cstdlib>
#include <filesystem>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <vix/cli/Style.hpp>
using namespace vix::cli::style;
namespace vix::cli::errors::runtime
{
namespace
{
enum class DeadlockKind
{
LockOrderInversion,
ResourceDeadlockAvoided,
SelfDeadlock,
RecursiveLock,
MutexCycle,
ThreadSanitizerDeadlock,
GenericDeadlock,
};
std::string trim_copy(const std::string &value)
{
std::size_t begin = 0;
while (begin < value.size() &&
std::isspace(
static_cast<unsigned char>(value[begin])) != 0)
{
++begin;
}
std::size_t end = value.size();
while (end > begin &&
std::isspace(
static_cast<unsigned char>(value[end - 1])) != 0)
{
--end;
}
return value.substr(begin, end - begin);
}
std::string lowercase_copy(std::string value)
{
for (char &character : value)
{
character = static_cast<char>(
std::tolower(
static_cast<unsigned char>(character)));
}
return value;
}
bool technical_details_enabled()
{
const char *level = std::getenv("VIX_LOG_LEVEL");
if (level == nullptr || *level == '\0')
return false;
const std::string value =
lowercase_copy(trim_copy(level));
return value == "debug" ||
value == "trace";
}
DeadlockKind classify_deadlock(
const std::string &log)
{
if (icontains(log, "lock-order-inversion") ||
icontains(log, "lock order inversion") ||
icontains(log, "cycle in lock order graph"))
{
return DeadlockKind::LockOrderInversion;
}
if (icontains(log, "resource deadlock avoided") ||
icontains(log, "EDEADLK") ||
icontains(log, "E DEADLK"))
{
return DeadlockKind::ResourceDeadlockAvoided;
}
if (icontains(log, "self-deadlock") ||
icontains(log, "self deadlock") ||
icontains(log, "would deadlock") ||
icontains(log, "already owns the mutex") ||
icontains(log, "mutex already locked by current thread"))
{
return DeadlockKind::SelfDeadlock;
}
if (icontains(log, "recursive lock attempt") ||
icontains(log, "recursive locking") ||
icontains(log, "recursive mutex lock"))
{
return DeadlockKind::RecursiveLock;
}
if (icontains(log, "ThreadSanitizer") &&
icontains(log, "deadlock"))
{
return DeadlockKind::ThreadSanitizerDeadlock;
}
if ((icontains(log, "mutex") ||
icontains(log, "lock")) &&
icontains(log, "cycle"))
{
return DeadlockKind::MutexCycle;
}
return DeadlockKind::GenericDeadlock;
}
std::string choose_message(
const std::string &log)
{
switch (classify_deadlock(log))
{
case DeadlockKind::LockOrderInversion:
return "mutexes were locked in conflicting orders";
case DeadlockKind::ResourceDeadlockAvoided:
return "locking this resource would cause a deadlock";
case DeadlockKind::SelfDeadlock:
return "thread tried to lock the same mutex twice";
case DeadlockKind::RecursiveLock:
return "mutex was locked recursively";
case DeadlockKind::MutexCycle:
return "mutex dependency cycle detected";
case DeadlockKind::ThreadSanitizerDeadlock:
return "ThreadSanitizer detected a deadlock";
case DeadlockKind::GenericDeadlock:
default:
return "deadlock detected";
}
}
std::string choose_description(
const std::string &log)
{
switch (classify_deadlock(log))
{
case DeadlockKind::LockOrderInversion:
return "Different threads acquired the same mutexes in a different order.";
case DeadlockKind::ResourceDeadlockAvoided:
return "The operation was stopped because the current locking sequence could not complete safely.";
case DeadlockKind::SelfDeadlock:
return "A non-recursive mutex was locked again by the thread that already owns it.";
case DeadlockKind::RecursiveLock:
return "The current code path entered another lock scope while still owning the same mutex.";
case DeadlockKind::MutexCycle:
return "Two or more lock dependencies form a cycle, so no waiting thread can continue.";
case DeadlockKind::ThreadSanitizerDeadlock:
return "ThreadSanitizer found a lock sequence that can block the involved threads permanently.";
case DeadlockKind::GenericDeadlock:
default:
return "One or more threads are waiting for resources that cannot become available.";
}
}
std::string choose_hint(
const std::string &log)
{
switch (classify_deadlock(log))
{
case DeadlockKind::LockOrderInversion:
return "always acquire the mutexes in the same order, or lock them together with std::scoped_lock";
case DeadlockKind::ResourceDeadlockAvoided:
return "check nested lock scopes and repeated lock() calls on the same mutex";
case DeadlockKind::SelfDeadlock:
return "remove the second lock or release the first lock before entering this code path";
case DeadlockKind::RecursiveLock:
return "prefer one lock scope; use std::recursive_mutex only when recursive ownership is intentional";
case DeadlockKind::MutexCycle:
return "break the cycle by defining one global order for acquiring shared resources";
case DeadlockKind::ThreadSanitizerDeadlock:
return "compare the lock acquisition traces and make every thread follow the same lock order";
case DeadlockKind::GenericDeadlock:
default:
return "use a consistent lock order and prefer std::scoped_lock when acquiring multiple mutexes";
}
}
std::string choose_secondary_hint(
const std::string &log)
{
switch (classify_deadlock(log))
{
case DeadlockKind::LockOrderInversion:
case DeadlockKind::MutexCycle:
case DeadlockKind::ThreadSanitizerDeadlock:
return "run with VIX_LOG_LEVEL=debug to inspect the complete lock traces";
case DeadlockKind::ResourceDeadlockAvoided:
case DeadlockKind::SelfDeadlock:
case DeadlockKind::RecursiveLock:
case DeadlockKind::GenericDeadlock:
default:
return {};
}
}
bool may_use_source_hint(
DeadlockKind kind)
{
/*
* A local source search is useful only when the error is
* probably caused by one repeated lock operation.
*
* Lock-order inversions and mutex cycles involve multiple
* locations. Highlighting the first lock() in the file would
* be misleading.
*/
switch (kind)
{
case DeadlockKind::ResourceDeadlockAvoided:
case DeadlockKind::SelfDeadlock:
case DeadlockKind::RecursiveLock:
return true;
case DeadlockKind::LockOrderInversion:
case DeadlockKind::MutexCycle:
case DeadlockKind::ThreadSanitizerDeadlock:
case DeadlockKind::GenericDeadlock:
default:
return false;
}
}
std::vector<std::string>
source_patterns_for_local_deadlock()
{
/*
* Keep only lock operations.
*
* Type declarations such as std::mutex, std::lock_guard and
* std::unique_lock are excluded because they can highlight
* unrelated declarations instead of the failing operation.
*/
return {
"std::lock(",
".lock(",
".try_lock(",
"pthread_mutex_lock(",
"pthread_mutex_trylock(",
};
}
bool looks_like_deadlock_log(
const std::string &log)
{
return icontains(log, "deadlock") ||
icontains(log, "resource deadlock avoided") ||
icontains(log, "EDEADLK") ||
icontains(log, "E DEADLK") ||
icontains(log, "lock-order-inversion") ||
icontains(log, "lock order inversion") ||
icontains(log, "cycle in lock order graph") ||
icontains(log, "would deadlock");
}
void print_error(
const std::string &message,
const std::string &description)
{
std::cerr << RED
<< "runtime error: "
<< message
<< RESET
<< "\n";
if (!description.empty())
{
std::cerr << " "
<< description
<< "\n";
}
}
void print_hints_and_location(
const std::string &hint,
const std::string &secondaryHint,
const RuntimeLocation &location)
{
std::vector<std::string> hints;
if (!hint.empty())
hints.push_back(hint);
if (!secondaryHint.empty())
hints.push_back(secondaryHint);
/*
* Do not fall back to "source: main.cpp".
*
* A filename without a precise line is not a deadlock
* location.
*/
const std::string at =
location.valid()
? make_at_text(
location,
std::filesystem::path{})
: std::string{};
if (hints.empty() && at.empty())
return;
std::cerr << "\n";
print_runtime_hints_and_at(
hints,
at);
}
void print_debug_log(
const std::string &log)
{
if (!technical_details_enabled())
return;
/*
* Deadlock reports may contain multiple lock stacks and a
* lock dependency graph. Keep them available in debug mode.
*/
print_runtime_log_excerpt(
log,
24);
}
} // namespace
class DeadlockRule final
: public IRuntimeErrorRule
{
public:
bool match(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
(void)sourceFile;
return looks_like_deadlock_log(log);
}
bool handle(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
const DeadlockKind kind =
classify_deadlock(log);
const std::string message =
choose_message(log);
const std::string description =
choose_description(log);
const std::string hint =
choose_hint(log);
const std::string secondaryHint =
choose_secondary_hint(log);
RuntimeLocation location =
find_best_runtime_location(
log,
sourceFile);
if (!location.valid() &&
may_use_source_hint(kind))
{
location =
find_best_runtime_location_or_source_hint(
log,
sourceFile,
source_patterns_for_local_deadlock());
}
print_error(
message,
description);
if (location.valid())
{
std::cerr << "\n";
const auto error =
make_runtime_location(
location.file,
location.line,
location.column,
message);
print_runtime_codeframe(error);
}
print_hints_and_location(
hint,
secondaryHint,
location);
print_debug_log(log);
return true;
}
};
std::unique_ptr<IRuntimeErrorRule>
makeDeadlockRule()
{
return std::make_unique<DeadlockRule>();
}
} // namespace vix::cli::errors::runtime