Improper nesting of OpenMP* CRITICAL directives

CRITICAL directives with the same name must not be dynamically nested.

The CRITICAL directive establishes a critical region with a given name. This ensures that only one thread can execute the region at a time. Unlike critical sections in the native threading libraries, OpenMP* critical sections are not reentrant. That is, if the same physical thread attempts to enter the critical region twice without leaving first then it would deadlock with itself.

ID	Code Location	Description
1	OpenMP usage error	The place where the CRITICAL directive that is executed second (illegally)
2	Definition	The place where the CRITICAL directive is executed first (legally)

Example

          
#include <stdio.h>

void mysub(int ii, int * jj) {
    // bad nesting here
    #pragma omp critical (sum)
    *jj += ii;
}
 
int main(int argc, char **argv)
{
    int i, j;
 
    #pragma omp parallel for private(j) ordered
    for (i = 1; i < 10; i++) {
        j = 0;
        
        #pragma omp critical (not_sum)
        mysub(i, &j);
        
        #pragma omp critical (sum)
        mysub(i, &j);
        
        #pragma omp ordered
        printf("%d\n", j);
    }
    return 0;
}