src/patches/cyrus-imapd-2.1.3-flock.patch

   1 --- cyrus-imapd-2.1.3/lib/lock_flock.c  Tue Oct  2 16:08:13 2001
   2 +++ cyrus-imapd-2.1.3-patched/lib/lock_flock.c  Tue Apr 16 09:44:58 2002
   3 @@ -51,6 +51,10 @@
   4  #endif
   5
   6  #include "lock.h"
   7 +#include <syslog.h>
   8 +
   9 +/* Locking timeout parameter */
  10 +#define MAXTIME 99
  11
  12  const char *lock_method_desc = "flock";
  13
  14 @@ -69,6 +73,18 @@
  15   * 'failaction' is provided, it is filled in with a pointer to a fixed
  16   * string naming the action that failed.
  17   *
  18 + *  Modified by jwade 4/16/2002 to work around seen file locking problem
  19 + *  Added locking timeout parameter to allow processes that are
  20 + *  waiting for a lock to eventually time out
  21 + *
  22 + *  Calls flock() in non-blocking fashion and then retries until a
  23 + *  maximum delay is reached or the lock succeeds.
  24 + *
  25 + *  As written, uses a quadratic backoff on retries with MAXTIME being
  26 + *  the longest interval delay.   Total delay time is the sum of the squares
  27 + *  of all integers whose square is less than MAXTIME.  In the case of
  28 + *  MAXTIME = 99 this is 0+1+4+9+16+25+36+49+64+81= 285 Seconds
  29 + *  This time is arbitrary and can be adjusted
  30   */
  31  int lock_reopen(fd, filename, sbuf, failaction)
  32  int fd;
  33 @@ -79,17 +95,29 @@
  34      int r;
  35      struct stat sbuffile, sbufspare;
  36      int newfd;
  37 +    int delay=0, i=0;
  38
  39      if (!sbuf) sbuf = &sbufspare;
  40
  41 -    for (;;) {
  42 -       r = flock(fd, LOCK_EX);
  43 +    for(i=0,delay=0;;) {
  44 +       r = flock(fd, LOCK_EX|LOCK_NB);
  45         if (r == -1) {
  46 -           if (errno == EINTR) continue;
  47 -           if (failaction) *failaction = "locking";
  48 +           if (errno == EINTR) {
  49 +                 continue;
  50 +            }
  51 +            else if ((errno == EWOULDBLOCK) && (delay < MAXTIME)) {
  52 +                syslog(LOG_DEBUG, "lock: reopen-blocked sleeping for %d on interval %d (%d, %s)" , delay, i, fd, filename);
  53 +                sleep(delay);
  54 +                i++;
  55 +                delay = i*i;
  56 +                continue;
  57 +            }
  58 +           if (failaction) {
  59 +                if (delay >= MAXTIME) *failaction = "locking_timeout";
  60 +                else *failaction = "locking";
  61 +            }
  62             return -1;
  63         }
  64 -
  65         fstat(fd, sbuf);
  66         r = stat(filename, &sbuffile);
  67         if (r == -1) {
  68 @@ -97,9 +125,7 @@
  69             flock(fd, LOCK_UN);
  70             return -1;
  71         }
  72 -
  73         if (sbuf->st_ino == sbuffile.st_ino) return 0;
  74 -
  75         newfd = open(filename, O_RDWR);
  76         if (newfd == -1) {
  77             if (failaction) *failaction = "opening";