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File: [cvs.NetBSD.org] / src / sys / kern / kern_cfglock.c (download)

Revision 1.1, Sat Aug 21 13:17:31 2010 UTC (9 years, 3 months ago) by pgoyette
Branch: MAIN
CVS Tags: yamt-pagecache-tag8, yamt-pagecache-base9, yamt-pagecache-base8, yamt-pagecache-base7, yamt-pagecache-base6, yamt-pagecache-base5, yamt-pagecache-base4, yamt-pagecache-base3, yamt-pagecache-base2, yamt-pagecache-base, yamt-pagecache, yamt-nfs-mp-base11, uebayasi-xip-base4, uebayasi-xip-base3, tls-maxphys-base-20171202, tls-maxphys-base, tls-maxphys, tls-earlyentropy-base, tls-earlyentropy, rmind-uvmplock-nbase, rmind-uvmplock-base, rmind-smpnet-nbase, rmind-smpnet-base, rmind-smpnet, riastradh-xf86-video-intel-2-7-1-pre-2-21-15, riastradh-drm2-base3, riastradh-drm2-base2, riastradh-drm2-base1, riastradh-drm2-base, riastradh-drm2, prg-localcount2-base3, prg-localcount2-base2, prg-localcount2-base1, prg-localcount2-base, prg-localcount2, phil-wifi-base, phil-wifi-20191119, phil-wifi-20190609, phil-wifi, pgoyette-localcount-base, pgoyette-localcount-20170426, pgoyette-localcount-20170320, pgoyette-localcount-20170107, pgoyette-localcount-20161104, pgoyette-localcount-20160806, pgoyette-localcount-20160726, pgoyette-localcount, pgoyette-compat-merge-20190127, pgoyette-compat-base, pgoyette-compat-20190127, pgoyette-compat-20190118, pgoyette-compat-1226, pgoyette-compat-1126, pgoyette-compat-1020, pgoyette-compat-0930, pgoyette-compat-0906, pgoyette-compat-0728, pgoyette-compat-0625, pgoyette-compat-0521, pgoyette-compat-0502, pgoyette-compat-0422, pgoyette-compat-0415, pgoyette-compat-0407, pgoyette-compat-0330, pgoyette-compat-0322, pgoyette-compat-0315, pgoyette-compat, perseant-stdc-iso10646-base, perseant-stdc-iso10646, nick-nhusb-base-20170825, nick-nhusb-base-20170204, nick-nhusb-base-20161204, nick-nhusb-base-20161004, nick-nhusb-base-20160907, nick-nhusb-base-20160529, nick-nhusb-base-20160422, nick-nhusb-base-20160319, nick-nhusb-base-20151226, nick-nhusb-base-20150921, nick-nhusb-base-20150606, nick-nhusb-base-20150406, nick-nhusb-base, nick-nhusb, netbsd-9-base, netbsd-9, netbsd-8-base, netbsd-8-1-RELEASE, netbsd-8-1-RC1, netbsd-8-0-RELEASE, netbsd-8-0-RC2, netbsd-8-0-RC1, netbsd-8, netbsd-7-nhusb-base-20170116, netbsd-7-nhusb-base, netbsd-7-nhusb, netbsd-7-base, netbsd-7-2-RELEASE, netbsd-7-1-RELEASE, netbsd-7-1-RC2, netbsd-7-1-RC1, netbsd-7-1-2-RELEASE, netbsd-7-1-1-RELEASE, netbsd-7-1, netbsd-7-0-RELEASE, netbsd-7-0-RC3, netbsd-7-0-RC2, netbsd-7-0-RC1, netbsd-7-0-2-RELEASE, netbsd-7-0-1-RELEASE, netbsd-7-0, netbsd-7, netbsd-6-base, netbsd-6-1-RELEASE, netbsd-6-1-RC4, netbsd-6-1-RC3, netbsd-6-1-RC2, netbsd-6-1-RC1, netbsd-6-1-5-RELEASE, netbsd-6-1-4-RELEASE, netbsd-6-1-3-RELEASE, netbsd-6-1-2-RELEASE, netbsd-6-1-1-RELEASE, netbsd-6-1, netbsd-6-0-RELEASE, netbsd-6-0-RC2, netbsd-6-0-RC1, netbsd-6-0-6-RELEASE, netbsd-6-0-5-RELEASE, netbsd-6-0-4-RELEASE, netbsd-6-0-3-RELEASE, netbsd-6-0-2-RELEASE, netbsd-6-0-1-RELEASE, netbsd-6-0, netbsd-6, matt-nb8-mediatek-base, matt-nb8-mediatek, matt-nb6-plus-nbase, matt-nb6-plus-base, matt-nb6-plus, matt-mips64-premerge-20101231, localcount-20160914, khorben-n900, jruoho-x86intr-base, jruoho-x86intr, jmcneill-usbmp-pre-base2, jmcneill-usbmp-base9, jmcneill-usbmp-base8, jmcneill-usbmp-base7, jmcneill-usbmp-base6, jmcneill-usbmp-base5, jmcneill-usbmp-base4, jmcneill-usbmp-base3, jmcneill-usbmp-base2, jmcneill-usbmp-base10, jmcneill-usbmp-base, jmcneill-usbmp, jmcneill-audiomp3-base, jmcneill-audiomp3, jdolecek-ncq-base, jdolecek-ncq, isaki-audio2-base, isaki-audio2, cherry-xenmp-base, cherry-xenmp, bouyer-socketcan-base1, bouyer-socketcan-base, bouyer-socketcan, bouyer-quota2-nbase, bouyer-quota2-base, bouyer-quota2, agc-symver-base, agc-symver, HEAD
Branch point for: yamt-nfs-mp, uebayasi-xip, rmind-uvmplock

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 !

/*	$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);
}