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Accelerated Linux Core Dump Analysis

Identify Active Threads

Explore techniques to identify and analyze active threads in Linux core dumps. This lesson helps you diagnose thread-specific issues such as arithmetic exceptions, corrupted instruction pointers, and potential stack overflows, enabling a deeper understanding of multi-threaded application crashes.

We'll cover the following...

We talked about multi-threaded applications throughout the course. In this lesson, we’ll learn how to identify active threads. We can take a look at all of the threads present in our application to find what’s causing this.

Application source code

We have created a multi-threaded application that encounters a divide-by-zero error and runs into a floating-point exception:

C
//  Build:
// gcc main.c -pthread -static -o App7
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
void procF(int i)
{
    int buffer[1024] = {-1, 0, i + 1, 0, -1};
    procF(buffer[2]);
}
void procE()
{
    procF(1);
}
int procD(int a, int b)
{
    return a / b;
}
int procC()
{
    return procD(1, 0);
}
void procB(char *buffer)
{
    char data[100] = "My New Bigger Buffer";
    memcpy(buffer, data, sizeof(data));
}
void procA()
{
    char data[10] = "My Buffer";
    procB(data);
}
#define THREAD_DECLARE(num, func) void bar_##num() \
{ \
    sleep(10); \
    func; \
} \
\
void foo_##num() \
{ \
    bar_##num(); \
} \
\
void * thread_##num (void *arg) \
{ \
    foo_##num(); \
    \
    return 0; \
}
THREAD_DECLARE(one, procA())
THREAD_DECLARE(two, sleep(-1))
THREAD_DECLARE(three, procC())
THREAD_DECLARE(four, sleep(-1))
THREAD_DECLARE(five, procE())
#define THREAD_CREATE(num) {pthread_t threadID_##num; pthread_create(&threadID_##num, NULL, thread_##num, NULL);}
int main(int argc, const char * argv[])
{
    THREAD_CREATE(one)
    THREAD_CREATE(two)
    THREAD_CREATE(three)
    THREAD_CREATE(four)
    THREAD_CREATE(five)    
    
    sleep(-1);
    return 0;
}

Loading the core dump

We will load the core dump file using the following command:

gdb -c core.App7 -se App7

The above command will output the following to the terminal:

List all the threads

...