CONCURRENCY.DL : Double Lock

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CodeSonar^® 9.2p0

CONFIDENTIAL

CodeSecure Inc

C and C++

Binaries

CONCURRENCY.DL : Double Lock

Summary

A mutex has been locked twice, but there is no intervening unlock.

For broader checking for double-locking phenomena, enable warning classes Locked Twice and Missing Lock Release.

Properties

Class Name

Double Lock

Significance

reliability

Mnemonic

CONCURRENCY.DL

Triggering Functions

A warning is triggered if a lock acquisition function is called to acquire a mutex that has definitely already been acquired.

For the purpose of this check:

The following functions are treated as acquiring a lock.
- Any function treated as a lock acquisition function by CodeSonar:
  - any library function that is recognized as a lock acquisition function because CodeSonar ships with a library model that identifies it as such, and
  - any function for which you have added a library model identifying it as a lock acquisition function.
The following functions are treated as releasing a lock.
- Any function treated as a lock release function by CodeSonar:
  - any library function that is recognized as a lock release function because CodeSonar ships with a library model that identifies it as such, and
  - any function for which you have added a library model identifying it as a lock release function.

Example

#include <pthread.h>

void dl_1(pthread_mutex_t lock){
  pthread_mutex_lock(&lock);
  pthread_mutex_lock(&lock);     /* 'Double Lock' warning issued here. */
}

void dl_2(pthread_mutex_t lock){
  pthread_mutex_lock(&lock);
  pthread_mutex_unlock(&lock);
  pthread_mutex_lock(&lock);     /* 'Double Lock' warning issued here - pthread_mutex_unlock()
                                  *  may have failed to release the lock.
                                  */
}

int no_dl(pthread_mutex_t lock){
  if (!pthread_mutex_lock(&lock)){return -1;}
  if (!pthread_mutex_unlock(&lock)){return -1;}
  return pthread_mutex_lock(&lock);                /* ok: if control reaches this line,
                                                    * the call to pthread_mutex_unlock() must have succeeded
                                                    */
}

Notes

Trying to lock an already-locked mutex can cause deadlock or undefined behavior.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

To report problems with this documentation, please visit https://support.codesecure.com/.