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The C++ Standard, [thread.mutex.class], paragraph 5 [ISO/IEC 14882-2014], states the following:
The behavior of a program is undefined if it destroys a
mutexobject owned by any thread or a thread terminates while owning amutexobject.
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This compliant solution eliminates the race condition by extending the lifetime of the mutex:.
| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <mutex>
#include <thread>
const size_t maxThreads = 10;
void do_work(size_t i, std::mutex *pm) {
std::lock_guard<std::mutex> lk(*pm);
// Access data protected by the lock.
}
std::mutex m;
void start_threads() {
std::thread threads[maxThreads];
for (size_t i = 0; i < maxThreads; ++i) {
threads[i] = std::thread(do_work, i, &m);
}
}
|
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This compliant solution eliminates the race condition by joining the threads before the mutex's destructor is invoked:.
| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <mutex>
#include <thread>
const size_t maxThreads = 10;
void do_work(size_t i, std::mutex *pm) {
std::lock_guard<std::mutex> lk(*pm);
// Access data protected by the lock.
}
void run_threads() {
std::thread threads[maxThreads];
std::mutex m;
for (size_t i = 0; i < maxThreads; ++i) {
threads[i] = std::thread(do_work, i, &m);
}
for (size_t i = 0; i < maxThreads; ++i) {
threads[i].join();
}
} |
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Destroying a mutex while it is locked may result in invalid control flow and data corruption.
Rule | Severity | Likelihood |
|---|
Detectable | Repairable | Priority | Level |
|---|---|---|---|
CON50-CPP | Medium | Probable | No |
No | P4 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| CodeSonar |
| CONCURRENCY.LOCALARG | Local Variable Passed to Thread | ||||||
| Helix QAC |
| DF961, DF4962 | |||||||
| Klocwork |
| CERT.CONC.MUTEX.DESTROY_WHILE_LOCKED | |||||||
| Parasoft C/C++test |
| CERT_CPP-CON50-a | Do not destroy another thread's mutex | ||||||
| Polyspace Bug Finder |
| CERT C++: CON50-CPP | Checks for destruction of locked mutex (rule partially covered) |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
| MITRE CWE | CWE-667, Improper Locking |
| SEI CERT C Coding Standard | CON31-C. Do not destroy a mutex while it is locked |
Bibliography
| [ISO/IEC 14882-2014] | Subclause 30.4.1, "Mutex Requirements" |
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