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    SubjectRe: [PATCH] proc: readdir race fix (take 3)
    On Thursday 7 September 2006 00:43, Eric W. Biederman wrote:
    > Have you tested 2.6.18-rc6 without my patch?

    Yes I did, it didn't crash after a couple hours. Of course it doesn't
    prove anything as the crash appears to be the result of a race.

    I'll now apply Oleg's fix and see if things get better.

    > I guess the practical question is what was your test methodology to
    > reproduce this problem? A couple of more people running the same
    > test on a few more machines might at least give us confidence in what
    > is going on.

    "My" test program forks 1000 children who sleep for 1 second then look for
    themselves in /proc, warn if they can't find themselves, and exit. So
    basically the idea is that the process list will shrink very rapidly at
    the same moment every child does readdir(/proc).

    I attached the test program, I take no credit (nor shame) for it, it was
    provided to me by IBM (possibly on behalf of one of their own customers)
    as a way to demonstrate and reproduce the original readdir(/proc) race

    Jean Delvare
    #include <stdlib.h>
    #include <stdio.h>
    #include <dirent.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <sys/wait.h>
    #include <sys/param.h>
    #include <utmp.h>
    #include <pwd.h>
    #include <string.h>
    #include <unistd.h>
    #include <fcntl.h>
    #include <signal.h>
    #include <syslog.h>
    #include <errno.h>
    #include <stdarg.h>
    #include <ctype.h>

    #define NUM_CHILDREN 1000

    int i;
    DIR * dir = NULL;
    struct dirent *d;
    int pid;
    int mypid;

    mypid = getpid();

    if ((dir = opendir("/proc")) == (DIR *)0)
    perror("failed to open /proc\n");

    while((d = readdir(dir)) != (struct dirent *)0) {
    if ((pid = (pid_t)atoi(d->d_name)) == 0) continue;
    if (pid==mypid) return(1);
    printf("\nfailed to find myself: pid %d, iteration %d\n",mypid,i);

    int i;
    int pid;

    switch ((pid = fork())) {
    case 0: /* child */
    case -1: /* error */
    perror("failed to fork\n");
    default: /* parent */


    int i;
    (void)signal(SIGCHLD, SIG_IGN);

    for (i=0; i<NUM_CHILDREN; i++)

     \ /
      Last update: 2006-09-07 10:33    [W:0.023 / U:10.648 seconds]
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