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C

C static code analysis

Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code

  • All rules 315
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  • Quick Fix 19
Filtered: 6 rules found
multi-threading
    Impact
      Clean code attribute
        1. "pthread_mutex_t" should be unlocked in the reverse order they were locked

           Bug
        2. "pthread_mutex_t" should be properly initialized and destroyed

           Bug
        3. "pthread_mutex_t" should not be locked when already locked, or unlocked when already unlocked

           Bug
        4. Blocking functions should not be called inside critical sections

           Code Smell
        5. Local variables and member data should not be volatile

           Code Smell
        6. Non-reentrant POSIX functions should be replaced with their reentrant versions

           Code Smell

        Blocking functions should not be called inside critical sections

        intentionality - efficient
        maintainability
        Code Smell
        • cwe
        • symbolic-execution
        • multi-threading

        Blocking functions should not be called inside critical sections

        Why is this an issue?

        How can I fix it?

        More Info

        Concurrent accesses to shared resources are guarded by synchronization primitives such as mutexes to prevent data races. The section of code where a mutex is held is called the critical section. Critical sections are generally designed to be as small as possible, allowing concurrent threads to progress.

        It’s usually unintentional to perform blocking operations inside a critical section because the operation might block for long or even indefinitely, degrading performance or causing a deadlock.

        #include <cstdio>    // printf()
        #include <cstdlib>   // atoi()
        #include <mutex>
        #include <unistd.h>  // sleep()
        
        std::mutex m;
        int load_shared_resource(); // Guarded by mutex 'm'
        
        // Some time-intensive computation.
        void do_expensive_work(int value, FILE *fd) {
          char buf[4] = "";
          std::fgets(buf, sizeof(buf), fd);
          int sum = value + std::atoi(buf);
          std::printf("value + line: %d\n", sum);
        }
        
        void worker_thread(FILE *fd) {
          std::scoped_lock guard(m);
          int value = load_shared_resource();
          // Mutex 'm' could have been released here.
          do_expensive_work(value, fd);
        } // Mutex 'm' only released here, after 'do_expensive_work' is returned.
        

        Usually, blocking operations involve I/O operations, such as reading or writing a file or socket or sleeping for some specified time.

        What is the potential impact?

        Doing time-intensive operations while holding one or multiple locks will prevent concurrent threads from making progress updating the shared resource. This can lead to "bottlenecks" and the under-utilization of the hardware capabilities.

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