[OpenSIPS-Devel] [OpenSIPS/opensips] 000c65: load_balancer: Fix AB/BA deadlock in lb_start()

[Liviu Chircu]

  Branch: refs/heads/3.0
  Home:   https://github.com/OpenSIPS/opensips
  Commit: 000c6507e3912863ed16d46d3cabed9f5721da7c
      https://github.com/OpenSIPS/opensips/commit/000c6507e3912863ed16d46d3cabed9f5721da7c
  Author: Liviu Chircu <liviu at opensips.org>
  Date:   2020-09-03 (Thu, 03 Sep 2020)

  Changed paths:
    M modules/load_balancer/lb_data.c

  Log Message:
  -----------
  load_balancer: Fix AB/BA deadlock in lb_start()

Assuming we have resources A, B, before this patch we would have the
following lock grab order on the corresponding resource locks:
   (see lb_data.c +743):

    lb_start(): A, B
    lb_next(): B, A

This patch fixes this type of deadlock by inverting the resource AVP
elements, such that both functions grab the array locks identically:

    lb_start(): A, B
    lb_next(): A, B

(cherry picked from commit f4d5d31e9217b6c270f693d847fd714f019f2bb1)