svn commit: r341727 - head/sys/kern

[Mateusz Guzik]

Author: mjg
Date: Sat Dec  8 14:04:57 2018
New Revision: 341727
URL: https://svnweb.freebsd.org/changeset/base/341727

Log:
  umtx: avoid umtxshm locking on object termination if possible
  
  Sample build world result on tmpfs:
  kern.ipc.umtx_terminate_notempty: 0
  kern.ipc.umtx_terminate_empty: 2891815
  
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/kern/kern_umtx.c

Modified: head/sys/kern/kern_umtx.c
==============================================================================
--- head/sys/kern/kern_umtx.c	Sat Dec  8 12:52:09 2018	(r341726)
+++ head/sys/kern/kern_umtx.c	Sat Dec  8 14:04:57 2018	(r341727)
@@ -3796,6 +3796,9 @@ umtx_shm_object_terminated(vm_object_t object)
 	struct umtx_shm_reg *reg, *reg1;
 	bool dofree;
 
+	if (LIST_EMPTY(USHM_OBJ_UMTX(object)))
+		return;
+
 	dofree = false;
 	mtx_lock(&umtx_shm_lock);
 	LIST_FOREACH_SAFE(reg, USHM_OBJ_UMTX(object), ushm_obj_link, reg1) {