freebsd with flexible iflib nic queues
c552ebe12d
are handled in most CAM peripheral drivers that are not handled by GEOM's disk class. The usual character driver open and close semantics are that the driver gets N open calls, but only one close, when the last caller closes the device. CAM peripheral drivers expect that behavior to be honored to the letter, and the CAM peripheral driver code (specifically cam_periph_release_locked_busses()) panics if it is done incorrectly. Since devfs has to drop its locks while it calls a driver's close routine, and it does not have a way to delay or prevent open calls while it is calling the close routine, there is a race. The sequence of events, simplified a bit, is: - devfs acquires a lock - devfs checks the reference count, and if it is 1, continues to close. - devfs releases the lock - 2nd process open call on the device happens here - devfs calls the driver's close routine - devfs acquires a lock - devfs decrements the reference count - devfs releases the lock - 2nd process close call on the device happens here At the second close, we get a panic in cam_periph_release_locked_busses(), complaining that peripheral has been released when the reference count is already 0. This is because we have gotten two closes in a row, which should not happen. The fix is to add the D_TRACKCLOSE flag to the driver's cdevsw, so that we get a close() call for each open(). That does happen reliably, so we can make sure that our reference counts are correct. Note that the sa(4) and pt(4) drivers only allow one context through the open routine. So these drivers aren't exposed to the same race condition. scsi_ch.c, scsi_enc.c, scsi_enc_internal.h, scsi_pass.c, scsi_sg.c: For these drivers, change the open() routine to increment the reference count for every open, and just decrement the reference count in the close. Call cam_periph_release_locked() in some scenarios to avoid additional lock and unlock calls. scsi_pt.c: Call cam_periph_release_locked() in some scenarios to avoid additional lock and unlock calls. MFC after: 3 days |
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| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
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