CONCURRENCY.LOCK.ORDER : Conflicting Lock Order

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CodeSonar^® 9.2p0

CONFIDENTIAL

CodeSecure Inc

C and C++

CONCURRENCY.LOCK.ORDER : Conflicting Lock Order

Summary

Different threads acquire the same locks in different orders. This can lead to deadlock or other undefined behavior.

Properties

Class Name

Conflicting Lock Order

Significance

reliability

Mnemonic

CONCURRENCY.LOCK.ORDER

Categories

MisraC2025	MisraC2025:22.16	All mutex objects locked by a thread shall be explicitly unlocked by the same thread
MisraC2023	MisraC2023:22.16	All mutex objects locked by a thread shall be explicitly unlocked by the same thread
Misra2012	Misra2012:22.16	All mutex objects locked by a thread shall be explicitly unlocked by the same thread
CWE	CWE:413	Improper Resource Locking
	CWE:696	Incorrect Behavior Order
CERT-C	CERT-C:CON35-C	Avoid deadlock by locking in a predefined order
	CERT-C:POS51-C	Avoid deadlock with POSIX threads by locking in predefined order
CERT-CPP	CERT-CPP:CON53-CPP	Avoid deadlock by locking in a predefined order
JPL	JPL:9	Place restrictions on the use of semaphores and locks.

Availability

Available for C and C++.

Enabling

Checks for this warning class are disabled by default. To enable them, add the following WARNING_FILTER rule to the project configuration file.

WARNING_FILTER += allow class="Conflicting Lock Order"

Triggering Functions

Conflicting Lock Order warnings can be triggered by the following functions.

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.
Any function specified with the LOCK_FUNCTIONS configuration file parameter.

Example

#include <pthread.h>

pthread_mutex_t Green;
pthread_mutex_t Blue;


/* ----- Thread 1 ----- */
void green_before_blue(void){
    pthread_mutex_lock(&Green);                        /* Green acquired before Blue */
    pthread_mutex_lock(&Blue);  /* 'Conflicting Lock Order' warning issued either here or in marked location below */
    /* ... operate on locked data */
    pthread_mutex_unlock(&Blue);
    pthread_mutex_unlock(&Green);
}

/* ----- Thread 2 ----- */
void blue_before_green(void){
    pthread_mutex_lock(&Blue);                         /* Blue acquired before Green */
    pthread_mutex_lock(&Green);  /* 'Conflicting Lock Order' warning issued either here or in marked location above */
    /* ... operate on locked data */
    pthread_mutex_unlock(&Green);
    pthread_mutex_unlock(&Blue);
}

In a multithreaded environment, two threads could try to obtain the two locks in different orders, possibly resulting in deadlock:

Relevant Configuration File Parameters

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

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