Module Name: src
Committed By: rmind
Date: Sun Dec 20 23:00:59 UTC 2009
Modified Files:
src/sys/kern: sys_select.c
Log Message:
Add comment about locking.
To generate a diff of this commit:
cvs rdiff -u -r1.20 -r1.21 src/sys/kern/sys_select.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/sys_select.c
diff -u src/sys/kern/sys_select.c:1.20 src/sys/kern/sys_select.c:1.21
--- src/sys/kern/sys_select.c:1.20 Sat Dec 12 17:47:05 2009
+++ src/sys/kern/sys_select.c Sun Dec 20 23:00:59 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: sys_select.c,v 1.20 2009/12/12 17:47:05 dsl Exp $ */
+/* $NetBSD: sys_select.c,v 1.21 2009/12/20 23:00:59 rmind Exp $ */
/*-
* Copyright (c) 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -66,11 +66,25 @@
*/
/*
- * System calls relating to files.
+ * System calls of synchronous I/O multiplexing subsystem.
+ *
+ * Locking
+ *
+ * Two locks are used: <object-lock> and selcpu_t::sc_lock.
+ *
+ * The <object-lock> might be a device driver or another subsystem, e.g.
+ * socket or pipe. This lock is not exported, and thus invisible to this
+ * subsystem. Mainly, synchronisation between selrecord() and selnotify()
+ * routines depends on this lock, as it will be described in the comments.
+ *
+ * Lock order
+ *
+ * <object-lock> ->
+ * selcpu_t::sc_lock
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.20 2009/12/12 17:47:05 dsl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.21 2009/12/20 23:00:59 rmind Exp $");
#include <sys/param.h>
#include <sys/systm.h>
