068fbad288
Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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kernel | ||
lib | ||
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net | ||
samples | ||
scripts | ||
security | ||
sound | ||
usr | ||
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Makefile | ||
README | ||
REPORTING-BUGS |
Linux kernel release 2.6.xx <http://kernel.org/> These are the release notes for Linux version 2.6. Read them carefully, as they tell you what this is all about, explain how to install the kernel, and what to do if something goes wrong. WHAT IS LINUX? Linux is a clone of the operating system Unix, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance. It has all the features you would expect in a modern fully-fledged Unix, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and multistack networking including IPv4 and IPv6. It is distributed under the GNU General Public License - see the accompanying COPYING file for more details. ON WHAT HARDWARE DOES IT RUN? Although originally developed first for 32-bit x86-based PCs (386 or higher), today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell, IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS, Xtensa, AVR32 and Renesas M32R architectures. Linux is easily portable to most general-purpose 32- or 64-bit architectures as long as they have a paged memory management unit (PMMU) and a port of the GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has also been ported to a number of architectures without a PMMU, although functionality is then obviously somewhat limited. Linux has also been ported to itself. You can now run the kernel as a userspace application - this is called UserMode Linux (UML). DOCUMENTATION: - There is a lot of documentation available both in electronic form on the Internet and in books, both Linux-specific and pertaining to general UNIX questions. I'd recommend looking into the documentation subdirectories on any Linux FTP site for the LDP (Linux Documentation Project) books. This README is not meant to be documentation on the system: there are much better sources available. - There are various README files in the Documentation/ subdirectory: these typically contain kernel-specific installation notes for some drivers for example. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Changes file, as it contains information about the problems, which may result by upgrading your kernel. - The Documentation/DocBook/ subdirectory contains several guides for kernel developers and users. These guides can be rendered in a number of formats: PostScript (.ps), PDF, and HTML, among others. After installation, "make psdocs", "make pdfdocs", or "make htmldocs" will render the documentation in the requested format. INSTALLING the kernel: - If you install the full sources, put the kernel tarball in a directory where you have permissions (eg. your home directory) and unpack it: gzip -cd linux-2.6.XX.tar.gz | tar xvf - or bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf - Replace "XX" with the version number of the latest kernel. Do NOT use the /usr/src/linux area! This area has a (usually incomplete) set of kernel headers that are used by the library header files. They should match the library, and not get messed up by whatever the kernel-du-jour happens to be. - You can also upgrade between 2.6.xx releases by patching. Patches are distributed in the traditional gzip and the newer bzip2 format. To install by patching, get all the newer patch files, enter the top level directory of the kernel source (linux-2.6.xx) and execute: gzip -cd ../patch-2.6.xx.gz | patch -p1 or bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1 (repeat xx for all versions bigger than the version of your current source tree, _in_order_) and you should be ok. You may want to remove the backup files (xxx~ or xxx.orig), and make sure that there are no failed patches (xxx# or xxx.rej). If there are, either you or me has made a mistake. Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels (also known as the -stable kernels) are not incremental but instead apply directly to the base 2.6.x kernel. Please read Documentation/applying-patches.txt for more information. Alternatively, the script patch-kernel can be used to automate this process. It determines the current kernel version and applies any patches found. linux/scripts/patch-kernel linux The first argument in the command above is the location of the kernel source. Patches are applied from the current directory, but an alternative directory can be specified as the second argument. - If you are upgrading between releases using the stable series patches (for example, patch-2.6.xx.y), note that these "dot-releases" are not incremental and must be applied to the 2.6.xx base tree. For example, if your base kernel is 2.6.12 and you want to apply the 2.6.12.3 patch, you do not and indeed must not first apply the 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel version 2.6.12.2 and want to jump to 2.6.12.3, you must first reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying the 2.6.12.3 patch. You can read more on this in Documentation/applying-patches.txt - Make sure you have no stale .o files and dependencies lying around: cd linux make mrproper You should now have the sources correctly installed. SOFTWARE REQUIREMENTS Compiling and running the 2.6.xx kernels requires up-to-date versions of various software packages. Consult Documentation/Changes for the minimum version numbers required and how to get updates for these packages. Beware that using excessively old versions of these packages can cause indirect errors that are very difficult to track down, so don't assume that you can just update packages when obvious problems arise during build or operation. BUILD directory for the kernel: When compiling the kernel all output files will per default be stored together with the kernel source code. Using the option "make O=output/dir" allow you to specify an alternate place for the output files (including .config). Example: kernel source code: /usr/src/linux-2.6.N build directory: /home/name/build/kernel To configure and build the kernel use: cd /usr/src/linux-2.6.N make O=/home/name/build/kernel menuconfig make O=/home/name/build/kernel sudo make O=/home/name/build/kernel modules_install install Please note: If the 'O=output/dir' option is used then it must be used for all invocations of make. CONFIGURING the kernel: Do not skip this step even if you are only upgrading one minor version. New configuration options are added in each release, and odd problems will turn up if the configuration files are not set up as expected. If you want to carry your existing configuration to a new version with minimal work, use "make oldconfig", which will only ask you for the answers to new questions. - Alternate configuration commands are: "make config" Plain text interface. "make menuconfig" Text based color menus, radiolists & dialogs. "make xconfig" X windows (Qt) based configuration tool. "make gconfig" X windows (Gtk) based configuration tool. "make oldconfig" Default all questions based on the contents of your existing ./.config file and asking about new config symbols. "make silentoldconfig" Like above, but avoids cluttering the screen with questions already answered. "make defconfig" Create a ./.config file by using the default symbol values from arch/$ARCH/defconfig. "make allyesconfig" Create a ./.config file by setting symbol values to 'y' as much as possible. "make allmodconfig" Create a ./.config file by setting symbol values to 'm' as much as possible. "make allnoconfig" Create a ./.config file by setting symbol values to 'n' as much as possible. "make randconfig" Create a ./.config file by setting symbol values to random values. The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also use the environment variable KCONFIG_ALLCONFIG to specify a filename that contains config options that the user requires to be set to a specific value. If KCONFIG_ALLCONFIG=filename is not used, "make *config" checks for a file named "all{yes/mod/no/random}.config" for symbol values that are to be forced. If this file is not found, it checks for a file named "all.config" to contain forced values. NOTES on "make config": - having unnecessary drivers will make the kernel bigger, and can under some circumstances lead to problems: probing for a nonexistent controller card may confuse your other controllers - compiling the kernel with "Processor type" set higher than 386 will result in a kernel that does NOT work on a 386. The kernel will detect this on bootup, and give up. - A kernel with math-emulation compiled in will still use the coprocessor if one is present: the math emulation will just never get used in that case. The kernel will be slightly larger, but will work on different machines regardless of whether they have a math coprocessor or not. - the "kernel hacking" configuration details usually result in a bigger or slower kernel (or both), and can even make the kernel less stable by configuring some routines to actively try to break bad code to find kernel problems (kmalloc()). Thus you should probably answer 'n' to the questions for "development", "experimental", or "debugging" features. COMPILING the kernel: - Make sure you have at least gcc 3.2 available. For more information, refer to Documentation/Changes. Please note that you can still run a.out user programs with this kernel. - Do a "make" to create a compressed kernel image. It is also possible to do "make install" if you have lilo installed to suit the kernel makefiles, but you may want to check your particular lilo setup first. To do the actual install you have to be root, but none of the normal build should require that. Don't take the name of root in vain. - If you configured any of the parts of the kernel as `modules', you will also have to do "make modules_install". - Keep a backup kernel handy in case something goes wrong. This is especially true for the development releases, since each new release contains new code which has not been debugged. Make sure you keep a backup of the modules corresponding to that kernel, as well. If you are installing a new kernel with the same version number as your working kernel, make a backup of your modules directory before you do a "make modules_install". Alternatively, before compiling, use the kernel config option "LOCALVERSION" to append a unique suffix to the regular kernel version. LOCALVERSION can be set in the "General Setup" menu. - In order to boot your new kernel, you'll need to copy the kernel image (e.g. .../linux/arch/i386/boot/bzImage after compilation) to the place where your regular bootable kernel is found. - Booting a kernel directly from a floppy without the assistance of a bootloader such as LILO, is no longer supported. If you boot Linux from the hard drive, chances are you use LILO which uses the kernel image as specified in the file /etc/lilo.conf. The kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or /boot/bzImage. To use the new kernel, save a copy of the old image and copy the new image over the old one. Then, you MUST RERUN LILO to update the loading map!! If you don't, you won't be able to boot the new kernel image. Reinstalling LILO is usually a matter of running /sbin/lilo. You may wish to edit /etc/lilo.conf to specify an entry for your old kernel image (say, /vmlinux.old) in case the new one does not work. See the LILO docs for more information. After reinstalling LILO, you should be all set. Shutdown the system, reboot, and enjoy! If you ever need to change the default root device, video mode, ramdisk size, etc. in the kernel image, use the 'rdev' program (or alternatively the LILO boot options when appropriate). No need to recompile the kernel to change these parameters. - Reboot with the new kernel and enjoy. IF SOMETHING GOES WRONG: - If you have problems that seem to be due to kernel bugs, please check the file MAINTAINERS to see if there is a particular person associated with the part of the kernel that you are having trouble with. If there isn't anyone listed there, then the second best thing is to mail them to me (torvalds@linux-foundation.org), and possibly to any other relevant mailing-list or to the newsgroup. - In all bug-reports, *please* tell what kernel you are talking about, how to duplicate the problem, and what your setup is (use your common sense). If the problem is new, tell me so, and if the problem is old, please try to tell me when you first noticed it. - If the bug results in a message like unable to handle kernel paging request at address C0000010 Oops: 0002 EIP: 0010:XXXXXXXX eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx ds: xxxx es: xxxx fs: xxxx gs: xxxx Pid: xx, process nr: xx xx xx xx xx xx xx xx xx xx xx or similar kernel debugging information on your screen or in your system log, please duplicate it *exactly*. The dump may look incomprehensible to you, but it does contain information that may help debugging the problem. The text above the dump is also important: it tells something about why the kernel dumped code (in the above example it's due to a bad kernel pointer). More information on making sense of the dump is in Documentation/oops-tracing.txt - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump as is, otherwise you will have to use the "ksymoops" program to make sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred). This utility can be downloaded from ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ . Alternately you can do the dump lookup by hand: - In debugging dumps like the above, it helps enormously if you can look up what the EIP value means. The hex value as such doesn't help me or anybody else very much: it will depend on your particular kernel setup. What you should do is take the hex value from the EIP line (ignore the "0010:"), and look it up in the kernel namelist to see which kernel function contains the offending address. To find out the kernel function name, you'll need to find the system binary associated with the kernel that exhibited the symptom. This is the file 'linux/vmlinux'. To extract the namelist and match it against the EIP from the kernel crash, do: nm vmlinux | sort | less This will give you a list of kernel addresses sorted in ascending order, from which it is simple to find the function that contains the offending address. Note that the address given by the kernel debugging messages will not necessarily match exactly with the function addresses (in fact, that is very unlikely), so you can't just 'grep' the list: the list will, however, give you the starting point of each kernel function, so by looking for the function that has a starting address lower than the one you are searching for but is followed by a function with a higher address you will find the one you want. In fact, it may be a good idea to include a bit of "context" in your problem report, giving a few lines around the interesting one. If you for some reason cannot do the above (you have a pre-compiled kernel image or similar), telling me as much about your setup as possible will help. Please read the REPORTING-BUGS document for details. - Alternately, you can use gdb on a running kernel. (read-only; i.e. you cannot change values or set break points.) To do this, first compile the kernel with -g; edit arch/i386/Makefile appropriately, then do a "make clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". You can now use all the usual gdb commands. The command to look up the point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes with the EIP value.) gdb'ing a non-running kernel currently fails because gdb (wrongly) disregards the starting offset for which the kernel is compiled.