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lock up under moderate to heavy load.
The status & command fields share a 32-bit longword. The programming
API of the eepro apparently requires that you update the command field
of a transmit slot that you've already given to the card. This means
the card could be updating the status field of the same longword at
the same time. Since alphas can only operate on 32-bit chunks of
memory, both the status & command fields are loaded from memory &
operated on in registers when the following line of C is executed:
sc->cbl_last->cb_command &= ~FXP_CB_COMMAND_S;
The race is caused by the card DMA'ing up the status at just the wrong
time -- after it has been loaded into a register & before it has been
written back. The old value of the status is written back, clobbering
the status the card just DMA'ed up. The fact that the card has sent
this frame is missed & the transmit engine appears to hang.
Luckily, as numerous people on the freebsd-alpha list pointed out, the
load-locked/store-conditional instructions used by the atomic
functions work with respect changes in memory due to I/O devices. We
now use them to safely update the command field.
Tested by: Bernd Walter <ticso@mail.cicely.de>
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| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| kerberosIV | ||
| lib | ||
| libexec | ||
| release | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.upgrade | ||
| 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 and the contents of /etc. 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 with config(8) is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/handbook/kernelconfig.html And in the config(8) man page. The sample kernel configuration files reside in the sys/i386/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 LINT contains entries for all possible devices, not just those commonly used, and is meant more as a general reference than an actual kernel configuration file (a kernel built from it wouldn't even run). Source Roadmap: --------------- bin System/User commands. contrib Packages contributed by 3rd parties. crypto Export controlled 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. kerberosIV Kerberos package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. sbin System commands. secure DES and DES-related utilities - NOT FOR EXPORT! 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/handbook/synching.html