--- cyrus-imapd-2.1.3/lib/lock_flock.c	Tue Oct  2 16:08:13 2001

+++ cyrus-imapd-2.1.3-patched/lib/lock_flock.c	Tue Apr 16 09:44:58 2002

@@ -51,6 +51,10 @@

 #endif

 #include "lock.h"

+#include <syslog.h>

+

+/* Locking timeout parameter */

+#define MAXTIME 99

 const char *lock_method_desc = "flock";

@@ -69,6 +73,18 @@

  * 'failaction' is provided, it is filled in with a pointer to a fixed

  * string naming the action that failed.

  *

+ *  Modified by jwade 4/16/2002 to work around seen file locking problem

+ *  Added locking timeout parameter to allow processes that are  

+ *  waiting for a lock to eventually time out

+ *

+ *  Calls flock() in non-blocking fashion and then retries until a 

+ *  maximum delay is reached or the lock succeeds.

+ *  

+ *  As written, uses a quadratic backoff on retries with MAXTIME being

+ *  the longest interval delay.   Total delay time is the sum of the squares

+ *  of all integers whose square is less than MAXTIME.  In the case of 

+ *  MAXTIME = 99 this is 0+1+4+9+16+25+36+49+64+81= 285 Seconds   

+ *  This time is arbitrary and can be adjusted

  */

 int lock_reopen(fd, filename, sbuf, failaction)

 int fd;

@@ -79,17 +95,29 @@

     int r;

     struct stat sbuffile, sbufspare;

     int newfd;

+    int delay=0, i=0;

     if (!sbuf) sbuf = &sbufspare;

-    for (;;) {

-	r = flock(fd, LOCK_EX);

+    for(i=0,delay=0;;) {

+	r = flock(fd, LOCK_EX|LOCK_NB);

 	if (r == -1) {

-	    if (errno == EINTR) continue;

-	    if (failaction) *failaction = "locking";

+	    if (errno == EINTR) {

+                 continue;

+            }

+            else if ((errno == EWOULDBLOCK) && (delay < MAXTIME)) {

+                syslog(LOG_DEBUG, "lock: reopen-blocked sleeping for %d on interval %d (%d, %s)" , delay, i, fd, filename);

+                sleep(delay);

+                i++;

+                delay = i*i;

+                continue;

+            }

+	    if (failaction) {

+                if (delay >= MAXTIME) *failaction = "locking_timeout";

+                else *failaction = "locking";

+            }

 	    return -1;

 	}

-

 	fstat(fd, sbuf);

 	r = stat(filename, &sbuffile);

 	if (r == -1) {

@@ -97,9 +125,7 @@

 	    flock(fd, LOCK_UN);

 	    return -1;

 	}

-

 	if (sbuf->st_ino == sbuffile.st_ino) return 0;

-

 	newfd = open(filename, O_RDWR);

 	if (newfd == -1) {

 	    if (failaction) *failaction = "opening";