svn commit: r338426 - head/sys/cam/ctl

[Edward Tomasz Napierala]

Author: trasz
Date: Sat Sep  1 16:16:40 2018
New Revision: 338426
URL: https://svnweb.freebsd.org/changeset/base/338426

Log:
  Try harder in cfiscsi_offline().  This is believed to be the workaround
  for the "ctld hanging on reload" problem observed in same cases under
  high load.  I'm not 100% sure it's _the_ fix, as the issue is rather hard
  to reproduce, but it was tested as part of a larger path and the problem
  disappeared.  It certainly shouldn't break anything.
  
  Now, technically, it shouldn't be needed.  Quoting mav@, "After
  ct->ct_online == 0 there should be no new sessions attached to the target.
  And if you see some problems abbout it, it may either mean that there are
  some races where single cfiscsi_session_terminate(cs) call may be lost,
  or as a guess while this thread was sleeping target was reenabbled and
  redisabled again".  Should such race be discovered and properly fixed
  in the future, than this and the followup two commits can be backed out.
  
  PR:		220175
  Reported by:	Eugene M. Zheganin <emz at norma.perm.ru>
  Tested by:	Eugene M. Zheganin <emz at norma.perm.ru>
  Discussed with:	mav
  Approved by:	re (gjb)
  MFC after:	2 weeks
  Sponsored by:	playkey.net

Modified:
  head/sys/cam/ctl/ctl_frontend_iscsi.c

Modified: head/sys/cam/ctl/ctl_frontend_iscsi.c
==============================================================================
--- head/sys/cam/ctl/ctl_frontend_iscsi.c	Sat Sep  1 16:13:56 2018	(r338425)
+++ head/sys/cam/ctl/ctl_frontend_iscsi.c	Sat Sep  1 16:16:40 2018	(r338426)
@@ -1447,11 +1447,11 @@ cfiscsi_offline(void *arg)
 	ct->ct_online = 0;
 	online = --softc->online;
 
-	TAILQ_FOREACH(cs, &softc->sessions, cs_next) {
-		if (cs->cs_target == ct)
-			cfiscsi_session_terminate(cs);
-	}
 	do {
+		TAILQ_FOREACH(cs, &softc->sessions, cs_next) {
+			if (cs->cs_target == ct)
+				cfiscsi_session_terminate(cs);
+		}
 		TAILQ_FOREACH(cs, &softc->sessions, cs_next) {
 			if (cs->cs_target == ct)
 				break;