CONC.SLEEP

Call to blocking function in critical section

The CONC.SLEEP checker finds instances of blocking functions in critical sections of code.

Vulnerability and risk

Until the blocking function is executed, locks aren't released and other threads may be blocked. These situations can result in unexpected behavior, so it's best to avoid calling blocking functions.

Vulnerable code example

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  #include <pthread.h>
  
  void foo(pthread_mutex_t *mutex) {
    pthread_mutex_lock(mutex);
    sleep(30000);
    pthread_mutex_unlock(mutex);
  }

Klocwork flags line 5 to indicate that the call to blocking function sleep occurs when the mutex was locked at line 4.

Related checkers

• CONC.DL
• CONC.NO_UNLOCK

External guidance

• CERT POS52-C: Do not perform operations that can block while holding a POSIX lock

Security training

Application security training materials provided by Secure Code Warrior.

• Race Conditions Training VideoTest your skills with a training example

Extension

This checker can be extended. The related knowledge base record kinds are:

• CONC.LOCK
• CONC.LOCK.TRY
• CONC.UNLOCK
• CONC.CONDSIGNAL
• CONC.CONDWAIT

See Tuning C/C++ analysis for more information.