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/*
 * This test checks a problem that occured while Pin was detaching from an application in probe mode. Pin spawns a
 * detach thread for doing the detach work and creates a child process for stopping the applicaiton while the detach
 * work is being done. The problem occured when the detach process exited and an application thread calling the
 * "wait" system call caught the exit status instead of the dedicated detach thread. This test replicates this
 * scenario:
 * The main thread creates a child process and a secondary thread, and then calls the wait system call.
 * The secondary thread tells Pin to detach. Once the detach is finished, it releases the child process and exits.
 * The child process waits to be released and exits.
 * The test fails if the main thread catches any child other than the one created from within the application.
 *
 * KNOWN LIMITATION: As of today (Jun 9, 2011), the parent of the application (which could also be an application
 *                   process), will receive notification when the detach-thread and the detach-process in Pin exit.
 *
 */

#include <cstdio>
#include <pthread.h>
#include <string>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <cstdlib>
#include <sched.h>
#include <unistd.h>

using std::string;

// return values for parent and child
enum retValues {         // VALUE   DESCRIPTION                                             WHO RETURNS THIS

    RET_SUCCESS = 0,     //   0     everything is OK                                        both parent and child
    RET_PIPE_ERROR,      //   1     pipe creation failed                                    parent
    RET_FORK_ERROR,      //   2     fork system call failed                                 parent
    RET_READ_ERROR,      //   3     read system call failed                                 child
    RET_WAIT_ERROR,      //   4     wait system call failed with errno other than EINTR     parent
    RET_ILLEGAL_CHILD    //   5     wait returned with pid other than the child             parent
};

const int READ = 0;
const int WRITE = 1;

// This function is replaced by the tool. When it is called, it detaches Pin.
extern "C" void TellPinToDetach(unsigned long *updateWhenReady)
{
    return;
}

// The child waits for the secondary thread to release it from the read() system call.
// This will (hopefully) allow the parent to wait for any unexpceted child processes spawned by Pin.
int doChild(int fd[]) {
    close(fd[WRITE]);
    char buf [2];
    int res = RET_SUCCESS;
    if (read(fd[READ], buf, 1) < 0) { // Wait here until detach is complete
        perror("CHILD APP ERROR: read failed");
        res = RET_READ_ERROR;
    }
    close(fd[READ]);
    return res;
}

// The secondary thread detaches Pin and only then releases the child process by closing the pipe.
void* doSecondaryThread(void* fd) {
    unsigned long pinDetached = false; // This will change to true by the tool after Pin has detached
    TellPinToDetach(&pinDetached);
    while (!pinDetached) {
        sched_yield();
    }
    close(((int*)fd)[WRITE]); // Close the WRITE end of the pipe to release the child
    return NULL;
}

// The parent spawns a secondary thread that synchronizes Pin's detach and the child's exit.
// After spawning the thread, the main thread waits until the child exits. If for any reason,
// it gets a different child process, an error is printed.
int doParent(pid_t child, int fd[]) {
    close(fd[READ]);
    int status;
    pid_t retCh = -1;
    pthread_t secTh;
    pthread_create (&secTh, 0, doSecondaryThread, fd);
    do {
        retCh = waitpid(0, &status, __WCLONE | __WALL);
        if (retCh < 0) { // handle system call error
            if (errno == EINTR) {
                continue;
            }
            perror("PARENT APP ERROR: wait failed");
            return RET_WAIT_ERROR;
        }
        else if (retCh != child) { // this means that we got a child created by Pin - not good!
            fprintf(stderr, "PARENT APP ERROR: wait returned with pid: %d, expecting child: %d\n", retCh, child);
            return RET_ILLEGAL_CHILD;
        }
    } while (!WIFEXITED(status));
    
    pthread_join(secTh, 0);
    
    return RET_SUCCESS;
}

int main() {
    int fd[2];
    
    if (pipe(fd) != 0) {
        perror("PARENT APP ERROR: pipe creation failed");
        return RET_PIPE_ERROR;
    }
    
    pid_t child = fork();
    
    if (child < 0) {
        perror("PARENT APP ERROR: fork failed");
        return RET_FORK_ERROR;
    }
    
    if (child == 0) { // child's code
        return doChild(fd);
    }
    else { // parent's code
        return doParent(child, fd);
    }
}
