(ITS#5370) race condition in slap_op_time()

[h.b.furuseth@usit.uio.no]

Full_Name: Hallvard B Furuseth
Version: HEAD, RE23, RE24
OS: 
URL: 
Submission from: (NULL) (129.240.6.233)
Submitted by: hallvard


slapd/operation.c:slap_op_time() can decrease last_time:

thread 1:   *t = slap_get_time();
<clock:     increment time()>
thread 2:   *t = slap_get_time();
thread 2:   with mutex lock: increment last_time, set last_incr = 0;
thread 1:   with mutex lock: decrement last_time, set last_incr = 0;

The simplest fix is to move the slap_get_time() call inside the
(global) slap_op_mutex lock.

However as far as I can tell, only the accesslog overlay uses
op->o_tincr, the value which needs the mutex.  And accesslog
calls slap_op_time() itself when it needs that value.
So maybe we should remove the op->o_tincr field.  Other calls
to slap_op_time() can be replaced with slap_get_time().