minix/tests/test70.c

   1 /* Test 70 - regression test for m_out vfs race condition.
   2  *
   3  * Regression test for vfs overwriting m_out fields by competing threads.
   4  * lseek() uses one of these fields too so this test performs concurrent
   5  * lseek()s to trigger this situation.
   6  *
   7  * The program consists of 2 processes, each seeking to different ranges in
   8  * a test file. The bug would return the wrong value in one of the messaeg
   9  * fields so the lseek() return value would be wrong sometimes.
  10  *
  11  * The first instance seeks from 0 to SEEKWINDOW, the other instance seeks
  12  * from SEEKWINDOW to SEEKWINDOW+SEEKWINDOW.
  13  */
  14
  15 #include <time.h>
  16 #include <sys/types.h>
  17 #include <sys/wait.h>
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <stdio.h>
  23
  24 #include "common.h"
  25
  26 #define SEEKWINDOW 1000
  27
  28 static int
  29 doseeks(int seekbase)
  30 {
  31         char template[30] = "tempfile.XXXXXXXX";
  32         int iteration, fd = mkstemp(template);
  33         int limit = seekbase + SEEKWINDOW;
  34
  35         /* make a temporary file, unlink it so it's always gone
  36          * afterwards, and make it the size we need.
  37          */
  38         if(fd < 0) { perror("mkstemp"); e(2); return 1; }
  39         if(unlink(template) < 0) { perror("unlink"); e(3); return 1; }
  40         if(ftruncate(fd, limit) < 0) { perror("ftruncate"); e(4); return 1; }
  41
  42         /* try lseek() lots of times with different arguments and make
  43          * sure we get the right return value back, while this happens
  44          * in a concurrent process too.
  45          */
  46 #define ITERATIONS 5000
  47         for(iteration = 0; iteration < ITERATIONS; iteration++) {
  48                 int o;
  49                 for(o = seekbase; o < limit; o++) {
  50                         int r;
  51                         if((r=lseek(fd, o, SEEK_SET)) != o) {
  52                                 if(r < 0) perror("lseek");
  53                                 fprintf(stderr, "%d/%d  %d != %d\n",
  54                                         iteration, ITERATIONS, r, o);
  55                                 e(5);
  56                                 return 1;
  57                         }
  58                 }
  59         }
  60
  61         return 0;
  62 }
  63
  64 int
  65 main(void)
  66 {
  67   start(70);
  68   pid_t f;
  69   int result;
  70
  71   if((f=fork()) < 0) { e(1); quit(); }
  72
  73   if(f == 0) { exit(doseeks(0)); }
  74
  75   if(doseeks(SEEKWINDOW)) { e(10); }
  76
  77   if (waitpid(f, &result, 0) == -1) e(11);
  78   if (WEXITSTATUS(result) != 0) e(12);
  79
  80   quit();
  81
  82   return(-1);                   /* impossible */
  83 }
  84