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From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 23 Jan 2009 22:40:35 +0000 (UTC)
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Subject: svn commit: r187656 - in head/sys: kern sys
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Author: jhb
Date: Fri Jan 23 22:40:35 2009
New Revision: 187656
URL: http://svn.freebsd.org/changeset/base/187656

Log:
  Add a flag to tag individual sysctl leaf nodes as MPSAFE and thus not
  needing Giant.
  
  Submitted by:	csjp (an older version)

Modified:
  head/sys/kern/kern_sysctl.c
  head/sys/sys/sysctl.h

Modified: head/sys/kern/kern_sysctl.c
==============================================================================
--- head/sys/kern/kern_sysctl.c	Fri Jan 23 22:13:30 2009	(r187655)
+++ head/sys/kern/kern_sysctl.c	Fri Jan 23 22:40:35 2009	(r187656)
@@ -1334,11 +1334,11 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
 	if (error != 0)
 		return (error);
 #endif
-
-	/* XXX: Handlers are not guaranteed to be Giant safe! */
-	mtx_lock(&Giant);
+	if (!(oid->oid_kind & CTLFLAG_MPSAFE))
+		mtx_lock(&Giant);
 	error = oid->oid_handler(oid, arg1, arg2, req);
-	mtx_unlock(&Giant);
+	if (!(oid->oid_kind & CTLFLAG_MPSAFE))
+		mtx_unlock(&Giant);
 
 	return (error);
 }

Modified: head/sys/sys/sysctl.h
==============================================================================
--- head/sys/sys/sysctl.h	Fri Jan 23 22:13:30 2009	(r187655)
+++ head/sys/sys/sysctl.h	Fri Jan 23 22:40:35 2009	(r187656)
@@ -84,6 +84,7 @@ struct ctlname {
 #define CTLFLAG_SKIP	0x01000000	/* Skip this sysctl when listing */
 #define CTLMASK_SECURE	0x00F00000	/* Secure level */
 #define CTLFLAG_TUN	0x00080000	/* Tunable variable */
+#define CTLFLAG_MPSAFE	0x00040000	/* Handler is MP safe */
 #define CTLFLAG_RDTUN	(CTLFLAG_RD|CTLFLAG_TUN)
 
 /*