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in devfs if a particular race condition is hit in the device pager code. This was a side effect of change 227530 which changed the device pager interface to call a new destructor routine for the cdev. That destructor routine, old_dev_pager_dtor(), takes a VM object handle. The object handle is cast to a struct cdev *, and passed into dev_rel(). That works in most cases, except the case in cdev_pager_allocate() where there is a race condition between two threads allocating an object backed by the same device. The loser of the race deallocates its object at the end of the function. The problem is that before inserting the object into the dev_pager_object_list, the object's handle is changed from the struct cdev pointer to the object's own address. This is to avoid conflicts with the winner of the race, which already inserted an object in the list with a handle that is a pointer to the same cdev structure. The object is then passed to vm_object_deallocate(), and eventually makes its way down to old_dev_pager_dtor(). That function passes the handle pointer (which is actually a VM object, not a struct cdev as usual) into dev_rel(). dev_rel() decrements the reference count in the assumed struct cdev (which happens to be 0), and that triggers the assertion in dev_rel() that the reference count is greater than or equal to 0. The fix is to add a cdev pointer to the VM object, and use that pointer when calling the cdev_pg_dtor() routine. vm_object.h: Add a struct cdev pointer to the VM object structure. device_pager.c: In cdev_pager_allocate(), populate the new cdev pointer. In dev_pager_dealloc(), use the new cdev pointer when calling the object's cdev_pg_dtor() routine. Reviewed by: kib Sponsored by: Spectra Logic Corporation MFC after: 1 week
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. cddl Various commands and libraries under the Common Development and Distribution License. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html