git.ozlabs.org Git - ccan/blob - ccan/tdb/test/lock-tracking.c

   1 /* We save the locks so we can reaquire them. */
   2 #include <unistd.h>
   3 #include <fcntl.h>
   4 #include <stdarg.h>
   5 #include <stdlib.h>
   6 #include <ccan/tap/tap.h>
   7 #include <ccan/tdb/tdb_private.h>
   8 #include "lock-tracking.h"
   9
  10 struct lock {
  11         struct lock *next;
  12         unsigned int off;
  13         unsigned int len;
  14         int type;
  15 };
  16 static struct lock *locks;
  17 int locking_errors = 0;
  18 bool suppress_lockcheck = false;
  19 bool nonblocking_locks;
  20 int locking_would_block = 0;
  21 void (*unlock_callback)(int fd);
  22
  23 int fcntl_with_lockcheck(int fd, int cmd, ... /* arg */ )
  24 {
  25         va_list ap;
  26         int ret, arg3;
  27         struct flock *fl;
  28         bool may_block = false;
  29
  30         if (cmd != F_SETLK && cmd != F_SETLKW) {
  31                 /* This may be totally bogus, but we don't know in general. */
  32                 va_start(ap, cmd);
  33                 arg3 = va_arg(ap, int);
  34                 va_end(ap);
  35
  36                 return fcntl(fd, cmd, arg3);
  37         }
  38
  39         va_start(ap, cmd);
  40         fl = va_arg(ap, struct flock *);
  41         va_end(ap);
  42
  43         if (cmd == F_SETLKW && nonblocking_locks) {
  44                 cmd = F_SETLK;
  45                 may_block = true;
  46         }
  47         ret = fcntl(fd, cmd, fl);
  48
  49         /* Detect when we failed, but might have been OK if we waited. */
  50         if (may_block && ret == -1 && (errno == EAGAIN || errno == EACCES)) {
  51                 locking_would_block++;
  52         }
  53
  54         if (fl->l_type == F_UNLCK) {
  55                 struct lock **l;
  56                 struct lock *old = NULL;
  57
  58                 for (l = &locks; *l; l = &(*l)->next) {
  59                         if ((*l)->off == fl->l_start
  60                             && (*l)->len == fl->l_len) {
  61                                 if (ret == 0) {
  62                                         old = *l;
  63                                         *l = (*l)->next;
  64                                         free(old);
  65                                 }
  66                                 break;
  67                         }
  68                 }
  69                 if (!old && !suppress_lockcheck) {
  70                         diag("Unknown unlock %u@%u - %i",
  71                              (int)fl->l_len, (int)fl->l_start, ret);
  72                         locking_errors++;
  73                 }
  74         } else {
  75                 struct lock *new, *i;
  76                 unsigned int fl_end = fl->l_start + fl->l_len;
  77                 if (fl->l_len == 0)
  78                         fl_end = (unsigned int)-1;
  79
  80                 /* Check for overlaps: we shouldn't do this. */
  81                 for (i = locks; i; i = i->next) {
  82                         unsigned int i_end = i->off + i->len;
  83                         if (i->len == 0)
  84                                 i_end = (unsigned int)-1;
  85
  86                         if (fl->l_start >= i->off && fl->l_start < i_end)
  87                                 break;
  88                         if (fl_end >= i->off && fl_end < i_end)
  89                                 break;
  90
  91                         /* tdb_allrecord_lock does this, handle adjacent: */
  92                         if (fl->l_start == i_end && fl->l_type == i->type) {
  93                                 if (ret == 0) {
  94                                         i->len = fl->l_len
  95                                                 ? i->len + fl->l_len
  96                                                 : 0;
  97                                 }
  98                                 goto done;
  99                         }
 100                 }
 101                 if (i) {
 102                         /* Special case: upgrade of allrecord lock. */
 103                         if (i->type == F_RDLCK && fl->l_type == F_WRLCK
 104                             && i->off == FREELIST_TOP
 105                             && fl->l_start == FREELIST_TOP
 106                             && i->len == 0
 107                             && fl->l_len == 0) {
 108                                 if (ret == 0)
 109                                         i->type = F_WRLCK;
 110                                 goto done;
 111                         }
 112                         if (!suppress_lockcheck) {
 113                                 diag("%s lock %u@%u overlaps %u@%u",
 114                                      fl->l_type == F_WRLCK ? "write" : "read",
 115                                      (int)fl->l_len, (int)fl->l_start,
 116                                      i->len, (int)i->off);
 117                                 locking_errors++;
 118                         }
 119                 }
 120
 121                 if (ret == 0) {
 122                         new = malloc(sizeof *new);
 123                         new->off = fl->l_start;
 124                         new->len = fl->l_len;
 125                         new->type = fl->l_type;
 126                         new->next = locks;
 127                         locks = new;
 128                 }
 129         }
 130 done:
 131         if (ret == 0 && fl->l_type == F_UNLCK && unlock_callback)
 132                 unlock_callback(fd);
 133         return ret;
 134 }
 135
 136 unsigned int forget_locking(void)
 137 {
 138         unsigned int num = 0;
 139         while (locks) {
 140                 struct lock *next = locks->next;
 141                 free(locks);
 142                 locks = next;
 143                 num++;
 144         }
 145         return num;
 146 }