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Re: New diagnostic routine - mutex_ownable()
On Mon, 1 May 2017, Paul Goyette wrote:
even when using expensive checks, it's best not to make them
more expensive than is really necessary.
I understand and agree.
From my reading of sys/lockdebug.h, kern/subr_lockdebug.c and
kern/kern_mutex.c it would appear that mutex_ownable() can become
int
mutex_ownable(kmutex_t mtx)
{
#ifdef DEBUG
MUTEX_WANTLOCK(mtx)
#endif
return 1;
}
Taylor pointed out privately that this won't quite work, since
lockdebug_wantlock() currently updates ld->ld_{ex,sh}want counters.
The attached diffs get around this by making the "shared" argument to
lockdebug_wantlock() have three values instead of two. A positive value
now refers to shwant, a zero value to exwant, and a negative value means
don't touch either counter! The new MUTEX_TESTLOCK() macro uses -1 for
the shared argument.
Diffs attached (including man-page and sets-lists updates) - please let
me know if this is acceptable.
+------------------+--------------------------+----------------------------+
| Paul Goyette | PGP Key fingerprint: | E-mail addresses: |
| (Retired) | FA29 0E3B 35AF E8AE 6651 | paul at whooppee dot com |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd dot org |
+------------------+--------------------------+----------------------------+
Index: share/man/man9/Makefile
===================================================================
RCS file: /cvsroot/src/share/man/man9/Makefile,v
retrieving revision 1.409
retrieving revision 1.409.2.3
diff -u -p -r1.409 -r1.409.2.3
--- share/man/man9/Makefile 15 Apr 2017 13:52:51 -0000 1.409
+++ share/man/man9/Makefile 30 Apr 2017 04:56:55 -0000 1.409.2.3
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.409 2017/04/15 13:52:51 kamil Exp $
+# $NetBSD: Makefile,v 1.409.2.3 2017/04/30 04:56:55 pgoyette Exp $
# Makefile for section 9 (kernel function and variable) manual pages.
@@ -32,7 +32,7 @@ MAN= accept_filter.9 accf_data.9 accf_ht
kcpuset.9 kernhist.9 klua_lock.9 klua_mod_register.9 kmem.9 kpause.9 \
kfilter_register.9 knote.9 \
kprintf.9 kthread.9 linedisc.9 lock.9 locking.9 log.9 ltsleep.9 \
- LWP_CACHE_CREDS.9 \
+ localcount.9 LWP_CACHE_CREDS.9 \
makeiplcookie.9 \
malloc.9 mb.9 mbuf.9 mca.9 memcmp.9 memcpy.9 memoryallocators.9 \
memmove.9 memset.9 \
@@ -119,6 +119,7 @@ MLINKS+=autoconf.9 config_search_loc.9 \
autoconf.9 config_attach_pseudo.9 \
autoconf.9 config_detach.9 \
autoconf.9 config_detach_children.9 \
+ autoconf.9 config_detach_release.9 \
autoconf.9 config_deactivate.9 \
autoconf.9 config_defer.9 \
autoconf.9 config_interrupts.9 \
@@ -515,6 +516,7 @@ MLINKS+=module.9 module_autoload.9 \
MLINKS+=mstohz.9 hztoms.9
MLINKS+=mutex.9 mutex_init.9 mutex.9 mutex_destroy.9 mutex.9 mutex_enter.9 \
mutex.9 mutex_exit.9 mutex.9 mutex_tryenter.9 mutex.9 mutex_owned.9 \
+ mutex.9 mutex_ownable.9 \
mutex.9 mutex_spin_enter.9 mutex.9 mutex_spin_exit.9
MLINKS+=m_tag.9 m_tag_copy.9 \
m_tag.9 m_tag_copy_chain.9 \
Index: share/man/man9/mutex.9
===================================================================
RCS file: /cvsroot/src/share/man/man9/mutex.9,v
retrieving revision 1.26
diff -u -p -r1.26 mutex.9
--- share/man/man9/mutex.9 4 Sep 2013 10:17:58 -0000 1.26
+++ share/man/man9/mutex.9 1 May 2017 10:53:44 -0000
@@ -1,4 +1,4 @@
-.\" $NetBSD: mutex.9,v 1.26 2013/09/04 10:17:58 skrll Exp $
+.\" $NetBSD: mutex.9,v 1.26.16.1 2017/04/30 04:56:55 pgoyette Exp $
.\"
.\" Copyright (c) 2007, 2009 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -36,6 +36,7 @@
.Nm mutex_destroy ,
.Nm mutex_enter ,
.Nm mutex_exit ,
+.Nm mutex_ownable ,
.Nm mutex_owned ,
.Nm mutex_spin_enter ,
.Nm mutex_spin_exit ,
@@ -52,6 +53,8 @@
.Ft void
.Fn mutex_exit "kmutex_t *mtx"
.Ft int
+.Fn mutex_ownable "kmutex_t *mtx"
+.Ft int
.Fn mutex_owned "kmutex_t *mtx"
.Ft void
.Fn mutex_spin_enter "kmutex_t *mtx"
@@ -172,6 +175,22 @@ if it is not already equal or higher.
Release a mutex.
The mutex must have been previously acquired by the caller.
Mutexes may be released out of order as needed.
+.It Fn mutex_ownable "mtx"
+.Pp
+When compiled with LOCKDEBUG (see
+.Xr options 4 ) ,
+ensure that the current process can successfully acquire mtx.
+If mtx is already owned by the current process, the system will panic
+with a "locking against myself" error.
+.Pp
+This function is needed because
+.Fn mutex_owned
+does not differentiate if a spin mutex is owned by the current process
+vs owned by another process.
+.Fn mutex_ownable
+is reasonably heavy-weight (since it acquires the mutex, possibly
+waiting for it), so should only be used with
+.Xr KDASSERT 9 .
.It Fn mutex_owned "mtx"
.Pp
For adaptive mutexes, return non-zero if the current LWP holds the mutex.
Index: distrib/sets/lists/comp/mi
===================================================================
RCS file: /cvsroot/src/distrib/sets/lists/comp/mi,v
retrieving revision 1.2125
retrieving revision 1.2125.2.3
diff -u -p -r1.2125 -r1.2125.2.3
--- distrib/sets/lists/comp/mi 20 Apr 2017 13:11:03 -0000 1.2125
+++ distrib/sets/lists/comp/mi 30 Apr 2017 04:56:55 -0000 1.2125.2.3
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.2125 2017/04/20 13:11:03 joerg Exp $
+# $NetBSD: mi,v 1.2125.2.3 2017/04/30 04:56:55 pgoyette Exp $
#
# Note: don't delete entries from here - mark them as "obsolete" instead.
./etc/mtree/set.comp comp-sys-root
@@ -2873,6 +2873,7 @@
./usr/include/sys/ksyms.h comp-c-include
./usr/include/sys/ktrace.h comp-c-include
./usr/include/sys/lkm.h comp-obsolete obsolete
+./usr/include/sys/localcount.h comp-c-include
./usr/include/sys/localedef.h comp-c-include
./usr/include/sys/lock.h comp-c-include
./usr/include/sys/lockf.h comp-c-include
@@ -10312,6 +10313,7 @@
./usr/share/man/cat9/config_defer.0 comp-sys-catman .cat
./usr/share/man/cat9/config_detach.0 comp-sys-catman .cat
./usr/share/man/cat9/config_detach_children.0 comp-sys-catman .cat
+./usr/share/man/cat9/config_detach_release.0 comp-sys-catman .cat
./usr/share/man/cat9/config_finalize_register.0 comp-sys-catman .cat
./usr/share/man/cat9/config_found.0 comp-sys-catman .cat
./usr/share/man/cat9/config_found_ia.0 comp-sys-catman .cat
@@ -10740,6 +10742,7 @@
./usr/share/man/cat9/le64enc.0 comp-sys-catman .cat
./usr/share/man/cat9/le64toh.0 comp-sys-catman .cat
./usr/share/man/cat9/linedisc.0 comp-sys-catman .cat
+./usr/share/man/cat9/localcount.0 comp-sys-catman .cat
./usr/share/man/cat9/lock.0 comp-sys-catman .cat
./usr/share/man/cat9/locking.0 comp-sys-catman .cat
./usr/share/man/cat9/lockinit.0 comp-sys-catman .cat
@@ -10833,6 +10836,7 @@
./usr/share/man/cat9/mutex_enter.0 comp-sys-catman .cat
./usr/share/man/cat9/mutex_exit.0 comp-sys-catman .cat
./usr/share/man/cat9/mutex_init.0 comp-sys-catman .cat
+./usr/share/man/cat9/mutex_ownable.0 comp-sys-catman .cat
./usr/share/man/cat9/mutex_owned.0 comp-sys-catman .cat
./usr/share/man/cat9/mutex_spin_enter.0 comp-sys-catman .cat
./usr/share/man/cat9/mutex_spin_exit.0 comp-sys-catman .cat
@@ -17774,6 +17778,7 @@
./usr/share/man/html9/config_defer.html comp-sys-htmlman html
./usr/share/man/html9/config_detach.html comp-sys-htmlman html
./usr/share/man/html9/config_detach_children.html comp-sys-htmlman html
+./usr/share/man/html9/config_detach_release.html comp-sys-htmlman html
./usr/share/man/html9/config_finalize_register.html comp-sys-htmlman html
./usr/share/man/html9/config_found.html comp-sys-htmlman html
./usr/share/man/html9/config_found_ia.html comp-sys-htmlman html
@@ -18181,6 +18186,7 @@
./usr/share/man/html9/le64enc.html comp-sys-htmlman html
./usr/share/man/html9/le64toh.html comp-sys-htmlman html
./usr/share/man/html9/linedisc.html comp-sys-htmlman html
+./usr/share/man/html9/localcount.html comp-sys-htmlman html
./usr/share/man/html9/lock.html comp-sys-htmlman html
./usr/share/man/html9/locking.html comp-sys-htmlman html
./usr/share/man/html9/lockinit.html comp-sys-htmlman html
@@ -18273,6 +18279,7 @@
./usr/share/man/html9/mutex_enter.html comp-sys-htmlman html
./usr/share/man/html9/mutex_exit.html comp-sys-htmlman html
./usr/share/man/html9/mutex_init.html comp-sys-htmlman html
+./usr/share/man/html9/mutex_ownable.html comp-sys-htmlman html
./usr/share/man/html9/mutex_owned.html comp-sys-htmlman html
./usr/share/man/html9/mutex_spin_enter.html comp-sys-htmlman html
./usr/share/man/html9/mutex_spin_exit.html comp-sys-htmlman html
@@ -25348,6 +25355,7 @@
./usr/share/man/man9/config_defer.9 comp-sys-man .man
./usr/share/man/man9/config_detach.9 comp-sys-man .man
./usr/share/man/man9/config_detach_children.9 comp-sys-man .man
+./usr/share/man/man9/config_detach_release.9 comp-sys-man .man
./usr/share/man/man9/config_finalize_register.9 comp-sys-man .man
./usr/share/man/man9/config_found.9 comp-sys-man .man
./usr/share/man/man9/config_found_ia.9 comp-sys-man .man
@@ -25776,6 +25784,7 @@
./usr/share/man/man9/le64enc.9 comp-sys-man .man
./usr/share/man/man9/le64toh.9 comp-sys-man .man
./usr/share/man/man9/linedisc.9 comp-sys-man .man
+./usr/share/man/man9/localcount.9 comp-sys-man .man
./usr/share/man/man9/lock.9 comp-sys-man .man
./usr/share/man/man9/locking.9 comp-sys-man .man
./usr/share/man/man9/lockinit.9 comp-sys-man .man
@@ -25869,6 +25878,7 @@
./usr/share/man/man9/mutex_enter.9 comp-sys-man .man
./usr/share/man/man9/mutex_exit.9 comp-sys-man .man
./usr/share/man/man9/mutex_init.9 comp-sys-man .man
+./usr/share/man/man9/mutex_ownable.9 comp-sys-man .man
./usr/share/man/man9/mutex_owned.9 comp-sys-man .man
./usr/share/man/man9/mutex_spin_enter.9 comp-sys-man .man
./usr/share/man/man9/mutex_spin_exit.9 comp-sys-man .man
Index: sys/sys/mutex.h
===================================================================
RCS file: /cvsroot/src/sys/sys/mutex.h,v
retrieving revision 1.20
retrieving revision 1.20.52.1
diff -u -p -r1.20 -r1.20.52.1
--- sys/sys/mutex.h 8 Feb 2010 09:54:27 -0000 1.20
+++ sys/sys/mutex.h 30 Apr 2017 04:56:55 -0000 1.20.52.1
@@ -1,4 +1,4 @@
-/* $NetBSD: mutex.h,v 1.20 2010/02/08 09:54:27 skrll Exp $ */
+/* $NetBSD: mutex.h,v 1.20.52.1 2017/04/30 04:56:55 pgoyette Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -204,6 +204,7 @@ void mutex_spin_exit(kmutex_t *);
int mutex_tryenter(kmutex_t *);
int mutex_owned(kmutex_t *);
+int mutex_ownable(kmutex_t *);
lwp_t *mutex_owner(kmutex_t *);
void mutex_obj_init(void);
Index: sys/rump/librump/rumpkern/locks.c
===================================================================
RCS file: /cvsroot/src/sys/rump/librump/rumpkern/locks.c,v
retrieving revision 1.73
diff -u -p -r1.73 locks.c
--- sys/rump/librump/rumpkern/locks.c 27 Jan 2017 09:50:47 -0000 1.73
+++ sys/rump/librump/rumpkern/locks.c 1 May 2017 10:53:55 -0000
@@ -1,4 +1,4 @@
-/* $NetBSD: locks.c,v 1.73 2017/01/27 09:50:47 ozaki-r Exp $ */
+/* $NetBSD: locks.c,v 1.73.4.2 2017/04/30 07:07:56 pgoyette Exp $ */
/*
* Copyright (c) 2007-2011 Antti Kantee. All Rights Reserved.
@@ -26,7 +26,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: locks.c,v 1.73 2017/01/27 09:50:47 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: locks.c,v 1.73.4.2 2017/04/30 07:07:56 pgoyette Exp $");
#include <sys/param.h>
#include <sys/kmem.h>
@@ -183,6 +183,16 @@ mutex_exit(kmutex_t *mtx)
__strong_alias(mutex_spin_exit,mutex_exit);
int
+mutex_ownable(kmutex_t *mtx)
+{
+
+#ifdef LOCKDEBUG
+ WANTLOCK(mtx, -1);
+#endif
+ return 1;
+}
+
+int
mutex_owned(kmutex_t *mtx)
{
Index: sys/kern/kern_mutex.c
===================================================================
RCS file: /cvsroot/src/sys/kern/kern_mutex.c,v
retrieving revision 1.64
diff -u -p -r1.64 kern_mutex.c
--- sys/kern/kern_mutex.c 26 Jan 2017 04:11:56 -0000 1.64
+++ sys/kern/kern_mutex.c 1 May 2017 10:53:59 -0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_mutex.c,v 1.64 2017/01/26 04:11:56 christos Exp $ */
+/* $NetBSD: kern_mutex.c,v 1.64.4.1 2017/04/30 04:56:55 pgoyette Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
#define __MUTEX_PRIVATE
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.64 2017/01/26 04:11:56 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.64.4.1 2017/04/30 04:56:55 pgoyette Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
@@ -75,6 +75,9 @@ __KERNEL_RCSID(0, "$NetBSD: kern_mutex.c
#define MUTEX_WANTLOCK(mtx) \
LOCKDEBUG_WANTLOCK(MUTEX_DEBUG_P(mtx), (mtx), \
(uintptr_t)__builtin_return_address(0), 0)
+#define MUTEX_TESTLOCK(mtx) \
+ LOCKDEBUG_WANTLOCK(MUTEX_DEBUG_P(mtx), (mtx), \
+ (uintptr_t)__builtin_return_address(0), -1)
#define MUTEX_LOCKED(mtx) \
LOCKDEBUG_LOCKED(MUTEX_DEBUG_P(mtx), (mtx), NULL, \
(uintptr_t)__builtin_return_address(0), 0)
@@ -831,6 +834,23 @@ mutex_owner(kmutex_t *mtx)
}
/*
+ * mutex_ownable:
+ *
+ * When compiled with DEBUG and LOCKDEBUG defined, ensure that
+ * the mutex is available. We cannot use !mutex_owned() since
+ * that won't work correctly for spin mutexes.
+ */
+int
+mutex_ownable(kmutex_t *mtx)
+{
+
+#ifdef LOCKDEBUG
+ MUTEX_TESTLOCK(mtx);
+#endif
+ return 1;
+}
+
+/*
* mutex_tryenter:
*
* Try to acquire the mutex; return non-zero if we did.
Index: sys/kern/subr_lockdebug.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_lockdebug.c,v
retrieving revision 1.55
diff -u -p -r1.55 subr_lockdebug.c
--- sys/kern/subr_lockdebug.c 26 Jan 2017 04:11:56 -0000 1.55
+++ sys/kern/subr_lockdebug.c 1 May 2017 10:54:03 -0000
@@ -454,9 +454,9 @@ lockdebug_wantlock(const char *func, siz
return;
}
}
- if (shared)
+ if (shared > 0)
ld->ld_shwant++;
- else
+ else if (shared == 0)
ld->ld_exwant++;
if (recurse) {
lockdebug_abort1(func, line, ld, s, "locking against myself",
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