[PAL/vm-common] Hang on a detached thread

[dimakuv]

Reproducer:

#include <stdio.h>

#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

typedef struct {
    int seconds;
} thread_data_t;

void* thread_func(void* arg) {
    thread_data_t* data = (thread_data_t*)arg;
    sleep(data->seconds);
    free(data);  // Free the allocated memory for thread data
    printf("exiting!\n");
    exit(2);
}

int main(void) {
    printf("Hello, world\n");

    pthread_t thread;
    thread_data_t* data = malloc(sizeof(thread_data_t));
    if (data == NULL) {
        perror("Failed to allocate memory");
        return 1;
    }
    data->seconds = 2;

    if (pthread_create(&thread, NULL, thread_func, data) != 0) {
        perror("Failed to create thread");
        free(data);
        return 1;
    }

    pthread_detach(thread);
    while(1);
    return 0;
}

The hang happens here:

gramine-tdx/libos/src/sys/libos_exit.c

Line 179 in b6e9723

while (!check_last_thread(/*mark_self_dead=*/false)) {

Reported by @dimstav23