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[src/trunk]: src Define a set of new kernel locking primitives to implement t...
details: https://anonhg.NetBSD.org/src/rev/de32dcd51fa2
branches: trunk
changeset: 757250:de32dcd51fa2
user: pgoyette <pgoyette%NetBSD.org@localhost>
date: Sat Aug 21 13:17:31 2010 +0000
description:
Define a set of new kernel locking primitives to implement the recursive
kernconfig_mutex. Update module subsystem to use this mutex rather than
its own internal (non-recursive) mutex. Make module_autoload() do its
own locking to be consistent with the rest of the module_xxx() calls.
Update module(9) man page appropriately.
As discussed on tech-kern over the last few weeks.
Welcome to NetBSD 5.99.39 !
diffstat:
share/man/man9/module.9 | 50 ++++++++++++-----
sys/conf/files | 3 +-
sys/kern/init_main.c | 5 +-
sys/kern/kern_cfglock.c | 101 +++++++++++++++++++++++++++++++++++
sys/kern/kern_module.c | 135 ++++++++++++++++++++++++++---------------------
sys/sys/module.h | 3 +-
sys/sys/param.h | 4 +-
sys/sys/systm.h | 7 ++-
8 files changed, 224 insertions(+), 84 deletions(-)
diffs (truncated from 716 to 300 lines):
diff -r 95397848b9d9 -r de32dcd51fa2 share/man/man9/module.9
--- a/share/man/man9/module.9 Sat Aug 21 13:12:15 2010 +0000
+++ b/share/man/man9/module.9 Sat Aug 21 13:17:31 2010 +0000
@@ -1,4 +1,4 @@
-.\" $NetBSD: module.9,v 1.17 2010/08/18 01:56:45 pgoyette Exp $
+.\" $NetBSD: module.9,v 1.18 2010/08/21 13:17:32 pgoyette Exp $
.\"
.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -27,7 +27,7 @@
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
-.Dd August 17, 2010
+.Dd August XXX, 2010
.Dt MODULE 9
.Os
.Sh NAME
@@ -86,6 +86,8 @@
.Vt modinfo_t
type resides within the module itself, and contains module header info.
.El
+.Pp
+The module subsystem is protected by the global kernconfig_mutex.
.Sh FUNCTIONS
.Bl -tag -width abcd
.It Fn MODULE "class" "name" "required"
@@ -362,21 +364,37 @@
Until this routine is called, modules can only be loaded if they were
built-in to the kernel image or provided by the boot loader.
.El
-.Sh LOCK PROTOCOL
-The
-.Nm
-subsystem is protected with the global
-.Vt module_mutex .
-This
-.Xr mutex 9
-must be acquired before calling any of these routines.
-As an exception, the
+.Sh PROGRAMMING CONSIDERATIONS
+The module subsystem is designed to be called recursively, but only within
+a single lwp.
+This permits one module's
+.Fn modcmd
+routine to load or unload other modules.
+.Pp
+A module is not permitted to load or unload itself.
+Attempts to load or unload a module from within its own
+.Fn modcmd
+routine will fail with
+.Er EEXIST
+or
+.Er EBUSY
+respectively.
+.Pp
+Although a module can be loaded by either
.Fn module_load
-routine acquires the mutex itself, so one does not need to acquire it
-before calling
-.Fn module_load .
-Loading of a module and its required modules occurs as an atomic
-operation, and either completely succeeds or completely fails.
+or
+.Fn module_autoload
+it is not possible for the module's
+.Fn modcmd
+routine to distinguish between the two methods.
+Any module which needs to ensure that it does not get auto-unloaded must
+either handle the
+.Dv MODULE_CMD_AUTOUNLOAD
+command in its
+.Fn modcmd
+routine, or use
+.Fn module_hold
+to increment its reference count.
.Sh CODE REFERENCES
This section describes places within the
.Nx
diff -r 95397848b9d9 -r de32dcd51fa2 sys/conf/files
--- a/sys/conf/files Sat Aug 21 13:12:15 2010 +0000
+++ b/sys/conf/files Sat Aug 21 13:17:31 2010 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: files,v 1.992 2010/07/07 01:09:39 chs Exp $
+# $NetBSD: files,v 1.993 2010/08/21 13:17:32 pgoyette Exp $
# @(#)files.newconf 7.5 (Berkeley) 5/10/93
version 20100430
@@ -1434,6 +1434,7 @@
file kern/init_sysent.c
file kern/kern_acct.c
file kern/kern_auth.c
+file kern/kern_cfglock.c
file kern/kern_clock.c
file kern/kern_condvar.c
file kern/kern_core.c coredump
diff -r 95397848b9d9 -r de32dcd51fa2 sys/kern/init_main.c
--- a/sys/kern/init_main.c Sat Aug 21 13:12:15 2010 +0000
+++ b/sys/kern/init_main.c Sat Aug 21 13:17:31 2010 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: init_main.c,v 1.422 2010/06/26 07:23:57 pgoyette Exp $ */
+/* $NetBSD: init_main.c,v 1.423 2010/08/21 13:17:31 pgoyette Exp $ */
/*-
* Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -97,7 +97,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: init_main.c,v 1.422 2010/06/26 07:23:57 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: init_main.c,v 1.423 2010/08/21 13:17:31 pgoyette Exp $");
#include "opt_ddb.h"
#include "opt_ipsec.h"
@@ -303,6 +303,7 @@
kernel_lock_init();
once_init();
mutex_init(&cpu_lock, MUTEX_DEFAULT, IPL_NONE);
+ kernconfig_lock_init();
/* Initialize the device switch tables. */
devsw_init();
diff -r 95397848b9d9 -r de32dcd51fa2 sys/kern/kern_cfglock.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/kern/kern_cfglock.c Sat Aug 21 13:17:31 2010 +0000
@@ -0,0 +1,101 @@
+/* $NetBSD: kern_cfglock.c,v 1.1 2010/08/21 13:17:31 pgoyette Exp $ */
+
+/*-
+ * Copyright (c) 2002, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
+ * NASA Ames Research Center, and by Andrew Doran.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__KERNEL_RCSID(0, "$NetBSD: kern_cfglock.c,v 1.1 2010/08/21 13:17:31 pgoyette Exp $");
+
+#include <sys/param.h>
+#include <sys/cpu.h>
+#include <sys/mutex.h>
+#include <sys/lwp.h>
+#include <sys/systm.h>
+
+static kmutex_t kernconfig_mutex;
+static lwp_t *kernconfig_lwp;
+static int kernconfig_recurse;
+
+/*
+ * Functions for manipulating the kernel configuration lock. This
+ * recursive lock should be used to protect all additions and removals
+ * of kernel functionality, such as device configuration and loading
+ * of modular kernel components.
+ */
+
+void
+kernconfig_lock_init(void)
+{
+
+ mutex_init(&kernconfig_mutex, MUTEX_DEFAULT, IPL_NONE);
+ kernconfig_lwp = NULL;
+ kernconfig_recurse = 0;
+}
+
+void
+kernconfig_lock(void)
+{
+ lwp_t *my_lwp;
+
+ /*
+ * It's OK to check this unlocked, since it could only be set to
+ * curlwp by the current thread itself, and not by an interrupt
+ * or any other LWP.
+ */
+ KASSERT(!cpu_intr_p());
+ my_lwp = curlwp;
+ if (kernconfig_lwp == my_lwp) {
+ kernconfig_recurse++;
+ KASSERT(kernconfig_recurse > 1);
+ } else {
+ mutex_enter(&kernconfig_mutex);
+ kernconfig_lwp = my_lwp;
+ kernconfig_recurse = 1;
+ }
+}
+
+void
+kernconfig_unlock(void)
+{
+
+ KASSERT(kernconfig_is_held());
+ KASSERT(kernconfig_recurse != 0);
+ if (--kernconfig_recurse == 0) {
+ kernconfig_lwp = NULL;
+ mutex_exit(&kernconfig_mutex);
+ }
+}
+
+bool
+kernconfig_is_held(void)
+{
+
+ return mutex_owned(&kernconfig_mutex);
+}
diff -r 95397848b9d9 -r de32dcd51fa2 sys/kern/kern_module.c
--- a/sys/kern/kern_module.c Sat Aug 21 13:12:15 2010 +0000
+++ b/sys/kern/kern_module.c Sat Aug 21 13:17:31 2010 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_module.c,v 1.71 2010/08/11 12:04:49 pgoyette Exp $ */
+/* $NetBSD: kern_module.c,v 1.72 2010/08/21 13:17:31 pgoyette Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_module.c,v 1.71 2010/08/11 12:04:49 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_module.c,v 1.72 2010/08/21 13:17:31 pgoyette Exp $");
#define _MODULE_INTERNAL
@@ -72,7 +72,6 @@
static int module_autoload_on = 1;
u_int module_count;
u_int module_builtinlist;
-kmutex_t module_lock;
u_int module_autotime = 10;
u_int module_gen = 1;
static kcondvar_t module_thread_cv;
@@ -223,7 +222,7 @@
modp[i] = module_newmodule(MODULE_SOURCE_KERNEL);
modp[i]->mod_info = mip[i+mipskip];
}
- mutex_enter(&module_lock);
+ kernconfig_lock();
/* do this in three stages for error recovery and atomicity */
@@ -263,7 +262,7 @@
}
out:
- mutex_exit(&module_lock);
+ kernconfig_unlock();
if (rv != 0) {
for (i = 0; i < nmodinfo; i++) {
if (modp[i])
@@ -291,13 +290,13 @@
if (rv)
return rv;
- mutex_enter(&module_lock);
+ kernconfig_lock();
rv = module_do_unload(mi->mi_name, true);
if (rv) {
goto out;
}
} else {
- mutex_enter(&module_lock);
+ kernconfig_lock();
}
TAILQ_FOREACH(mod, &module_builtins, mod_chain) {
if (strcmp(mod->mod_info->mi_name, mi->mi_name) == 0)
@@ -312,7 +311,7 @@
}
out:
- mutex_exit(&module_lock);
+ kernconfig_unlock();
return rv;
}
@@ -332,7 +331,6 @@
if (module_map == NULL) {
module_map = kernel_map;
}
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