Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261826AbUKHMd3 (ORCPT ); Mon, 8 Nov 2004 07:33:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261833AbUKHMd3 (ORCPT ); Mon, 8 Nov 2004 07:33:29 -0500 Received: from smtp002.mail.ukl.yahoo.com ([217.12.11.33]:25939 "HELO smtp002.mail.ukl.yahoo.com") by vger.kernel.org with SMTP id S261826AbUKHMc4 (ORCPT ); Mon, 8 Nov 2004 07:32:56 -0500 From: Karsten Wiese To: Andrew Morton Subject: Re: 2.6.10-rc1-mm3 Date: Mon, 8 Nov 2004 13:34:18 +0100 User-Agent: KMail/1.6.2 Cc: linux-kernel@vger.kernel.org, Ingo Molnar MIME-Version: 1.0 Content-Disposition: inline Content-Type: Multipart/Mixed; boundary="Boundary-00=_Kf2jBe24bWJcf9j" Message-Id: <200411081334.18751.annabellesgarden@yahoo.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 17811 Lines: 389 --Boundary-00=_Kf2jBe24bWJcf9j Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi This bug is triggered by logging on to bash (runlevel 3), typing "cat /proc/acpi", then gives the correct "/" to complete, the 2nd has no visual effect, the 3rd generates this oops: Unable to handle kernel paging request at virtual address f89e7b00 printing eip: c0187452 *pde = 37ff1067 *pte = 00000000 Oops: 0000 [#1] PREEMPT SMP Modules linked in: binfmt_misc video ohci1394 ieee1394 uhci_hcd intel_agp agpgart i2c_i801 i2c_core snd_emu10k1 snd_rawmidi snd_seq_device snd_ac97_codec snd_pcm snd_timer snd_page_alloc snd_util_mem snd_hwdep snd soundcore ext3 jbd ata_piix libata sd_mod scsi_mod CPU: 0 EIP: 0060:[] Not tainted VLI EFLAGS: 00010286 (2.6.10-rc1-mm3) EIP is at proc_get_inode+0xa0/0x184 eax: 00000000 ebx: f89e7b00 ecx: 00000001 edx: f7ee7000 esi: f62964bc edi: f66d6380 ebp: f7ee7de8 esp: f7ee7dc8 ds: 007b es: 007b ss: 0068 Process bash (pid: 5322, threadinfo=f7ee7000 task=f5d8c550) Stack: f62964bc f0000337 f7ee7de4 c02f3259 00000001 f66d6380 f4db2313 f66d63cf f7ee7e1c c018a0e6 f7f75200 f0000337 f66d6380 00000003 00000001 dead4ead ffffffea 00000000 fffffff4 f4db22a0 f5ea34bc f7ee7e3c c0169637 f5ea34bc Call Trace: [] show_stack+0x80/0x96 [] show_registers+0x161/0x1da [] die+0x107/0x190 [] do_page_fault+0x495/0x6cb [] error_code+0x2b/0x30 [] proc_lookup+0x7c/0xc4 [] real_lookup+0xab/0xc9 [] do_lookup+0x7d/0x88 [] link_path_walk+0x73e/0xef1 [] path_lookup+0x9a/0x163 [] __user_walk+0x2b/0x48 [] vfs_stat+0x1a/0x55 [] sys_stat64+0x19/0x38 [] sysenter_past_esp+0x52/0x71 Code: b7 47 0e 66 85 c0 74 06 0f b7 c0 89 46 2c 8b 5f 28 c7 45 f0 01 00 00 00 85 db 74 46 b8 01 00 00 00 e8 6a 54 f9 ff e8 9e 06 04 00 <83> 3b 02 0f 84 cf 00 00 00 c1 e0 07 01 d8 ff 80 00 01 00 00 b8 <6>note: bash[5322] exited with preempt_count 1 "cat /proc" and then works, so it is something about acpi? attached the complete dmesg output for reference. thanks, Karsten --Boundary-00=_Kf2jBe24bWJcf9j Content-Type: text/plain; charset="us-ascii"; name="2.6.10-rc1-mm3_cat_proc_acpi_TAB" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="2.6.10-rc1-mm3_cat_proc_acpi_TAB" Linux version 2.6.10-rc1-mm3 (root@p4.localdomain) (gcc-Version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)) #2 SMP Mon Nov 8 12:46:27 CET 2004 BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 000000003fe88c00 (usable) BIOS-e820: 000000003fe88c00 - 000000003fe8ac00 (ACPI NVS) BIOS-e820: 000000003fe8ac00 - 000000003fe8cc00 (ACPI data) BIOS-e820: 000000003fe8cc00 - 0000000040000000 (reserved) BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved) BIOS-e820: 00000000fec00000 - 00000000fed00400 (reserved) BIOS-e820: 00000000fed20000 - 00000000feda0000 (reserved) BIOS-e820: 00000000fee00000 - 00000000fef00000 (reserved) BIOS-e820: 00000000ffb00000 - 0000000100000000 (reserved) Warning only 896MB will be used. Use a HIGHMEM enabled kernel. 896MB LOWMEM available. found SMP MP-table at 000fe710 On node 0 totalpages: 229376 DMA zone: 4096 pages, LIFO batch:1 Normal zone: 225280 pages, LIFO batch:16 HighMem zone: 0 pages, LIFO batch:1 DMI 2.3 present. ACPI: RSDP (v000 DELL ) @ 0x000fec00 ACPI: RSDT (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fcc10 ACPI: FADT (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fcc50 ACPI: SSDT (v001 DELL st_ex 0x00001000 MSFT 0x0100000d) @ 0xfffc58e5 ACPI: MADT (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fccc4 ACPI: BOOT (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fcd36 ACPI: ASF! (v016 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fcd5e ACPI: MCFG (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fcdc5 ACPI: HPET (v001 DELL 4700 0x00000007 ASL 0x00000061) @ 0x000fce03 ACPI: DSDT (v001 DELL dt_ex 0x00001000 MSFT 0x0100000d) @ 0x00000000 ACPI: PM-Timer IO Port: 0x808 ACPI: Local APIC address 0xfee00000 ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled) Processor #0 15:3 APIC version 20 ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled) Processor #1 15:3 APIC version 20 ACPI: LAPIC (acpi_id[0x03] lapic_id[0x01] disabled) ACPI: LAPIC (acpi_id[0x04] lapic_id[0x07] disabled) ACPI: LAPIC_NMI (acpi_id[0xff] high level lint[0x1]) ACPI: IOAPIC (id[0x08] address[0xfec00000] gsi_base[0]) IOAPIC[0]: apic_id 8, version 32, address 0xfec00000, GSI 0-23 ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl) ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level) ACPI: IRQ0 used by override. ACPI: IRQ2 used by override. ACPI: IRQ9 used by override. Enabling APIC mode: Flat. Using 1 I/O APICs ACPI: HPET id: 0x8086a201 base: 0xfed00000 Using ACPI (MADT) for SMP configuration information Built 1 zonelists Initializing CPU#0 Kernel command line: ro root=LABEL=/ rhgb quiet 3 CPU 0 irqstacks, hard=c042f000 soft=c042d000 PID hash table entries: 4096 (order: 12, 65536 bytes) Console: colour VGA+ 80x25 Dentry cache hash table entries: 131072 (order: 7, 524288 bytes) Inode-cache hash table entries: 65536 (order: 6, 262144 bytes) Memory: 904752k/917504k available (2002k kernel code, 12072k reserved, 1023k data, 200k init, 0k highmem) Checking if this processor honours the WP bit even in supervisor mode... Ok. Using HPET for base-timer Using HPET for gettimeofday Detected 3192.287 MHz processor. Using hpet for high-res timesource Calibrating delay loop... 6324.22 BogoMIPS (lpj=3162112) Security Framework v1.0.0 initialized Mount-cache hash table entries: 512 (order: 0, 4096 bytes) CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 CPU: After vendor identify, caps: bfebfbff 00000000 00000000 00000000 monitor/mwait feature present. using mwait in idle threads. CPU: Trace cache: 12K uops, L1 D cache: 16K CPU: L2 cache: 1024K CPU: Physical Processor ID: 0 CPU: After all inits, caps: bfebfbff 00000000 00000000 00000080 Intel machine check architecture supported. Intel machine check reporting enabled on CPU#0. CPU0: Intel P4/Xeon Extended MCE MSRs (12) available Enabling fast FPU save and restore... done. Enabling unmasked SIMD FPU exception support... done. Checking 'hlt' instruction... OK. CPU0: Intel(R) Pentium(R) 4 CPU 3.20GHz stepping 04 per-CPU timeslice cutoff: 2925.53 usecs. task migration cache decay timeout: 3 msecs. Booting processor 1/1 eip 3000 CPU 1 irqstacks, hard=c0430000 soft=c042e000 Initializing CPU#1 Calibrating delay loop... 6373.37 BogoMIPS (lpj=3186688) CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 CPU: After vendor identify, caps: bfebfbff 00000000 00000000 00000000 monitor/mwait feature present. CPU: Trace cache: 12K uops, L1 D cache: 16K CPU: L2 cache: 1024K CPU: Physical Processor ID: 0 CPU: After all inits, caps: bfebfbff 00000000 00000000 00000080 Intel machine check architecture supported. Intel machine check reporting enabled on CPU#1. CPU1: Intel P4/Xeon Extended MCE MSRs (12) available CPU1: Intel(R) Pentium(R) 4 CPU 3.20GHz stepping 04 Total of 2 processors activated (12697.60 BogoMIPS). ENABLING IO-APIC IRQs ..TIMER: vector=0x31 pin1=2 pin2=-1 checking TSC synchronization across 2 CPUs: passed. Brought up 2 CPUs CPU0: domain 0: span 3 groups: 1 2 domain 1: span 3 groups: 3 CPU1: domain 0: span 3 groups: 2 1 domain 1: span 3 groups: 3 checking if image is initramfs... it is Freeing initrd memory: 463k freed NET: Registered protocol family 16 PCI: PCI BIOS revision 2.10 entry at 0xfb2cc, last bus=3 PCI: Using MMCONFIG mtrr: v2.0 (20020519) ACPI: Subsystem revision 20041015 ACPI: Interpreter enabled ACPI: Using IOAPIC for interrupt routing ACPI: PCI Root Bridge [PCI0] (00:00) PCI: Probing PCI hardware (bus 00) PCI: Ignoring BAR0-3 of IDE controller 0000:00:1f.1 PCI: Transparent bridge - 0000:00:1e.0 ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.PCI1._PRT] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.PCI2._PRT] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.PCI4._PRT] ACPI: PCI Interrupt Link [LNKA] (IRQs 3 4 5 6 7 9 10 *11 12 15) ACPI: PCI Interrupt Link [LNKB] (IRQs 3 4 *5 6 7 9 10 11 12 15) ACPI: PCI Interrupt Link [LNKC] (IRQs 3 4 *5 6 7 9 10 11 12 15) ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 6 7 9 10 11 12 15) *0, disabled. ACPI: PCI Interrupt Link [LNKE] (IRQs 3 4 5 6 7 *9 10 11 12 15) ACPI: PCI Interrupt Link [LNKF] (IRQs 3 4 5 6 7 9 *10 11 12 15) ACPI: PCI Interrupt Link [LNKG] (IRQs 3 4 5 6 7 *9 10 11 12 15) ACPI: PCI Interrupt Link [LNKH] (IRQs *3 4 5 6 7 9 10 11 12 15) usbcore: registered new driver usbfs usbcore: registered new driver hub PCI: Using ACPI for IRQ routing ** PCI interrupts are no longer routed automatically. If this ** causes a device to stop working, it is probably because the ** driver failed to call pci_enable_device(). As a temporary ** workaround, the "pci=routeirq" argument restores the old ** behavior. If this argument makes the device work again, ** please email the output of "lspci" to bjorn.helgaas@hp.com ** so I can fix the driver. Simple Boot Flag value 0x87 read from CMOS RAM was invalid Simple Boot Flag at 0x7a set to 0x1 IA-32 Microcode Update Driver: v1.14 Initializing Cryptographic API vesafb: probe of vesafb0 failed with error -6 ACPI: Power Button (FF) [PWRF] Real Time Clock Driver v1.12 [drm] Initialized drm 1.0.0 20040925 ACPI: PS/2 Keyboard Controller [KBD] at I/O 0x60, 0x64, irq 1 ACPI: PS/2 Mouse Controller [MOU] at irq 12 serio: i8042 AUX port at 0x60,0x64 irq 12 serio: i8042 KBD port at 0x60,0x64 irq 1 Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A io scheduler noop registered io scheduler anticipatory registered io scheduler deadline registered io scheduler cfq registered RAMDISK driver initialized: 16 RAM disks of 8192K size 1024 blocksize e100: Intel(R) PRO/100 Network Driver, 3.2.3-k2-NAPI e100: Copyright(c) 1999-2004 Intel Corporation ACPI: PCI interrupt 0000:03:08.0[A] -> GSI 20 (level, low) -> IRQ 20 e100: eth0: e100_probe: addr 0xdfcfb000, irq 20, MAC addr 00:11:11:65:15:D7 netconsole: not configured, aborting Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx ICH6: IDE controller at PCI slot 0000:00:1f.1 ACPI: PCI interrupt 0000:00:1f.1[A] -> GSI 16 (level, low) -> IRQ 16 ICH6: chipset revision 3 ICH6: not 100% native mode: will probe irqs later ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:pio Probing IDE interface ide0... hda: Philips DVD+RW DVD8601, ATAPI CD/DVD-ROM drive elevator: using anticipatory as default io scheduler ide0 at 0x1f0-0x1f7,0x3f6 on irq 14 Probing IDE interface ide1... ide1: Wait for ready failed before probe ! Probing IDE interface ide2... ide2: Wait for ready failed before probe ! Probing IDE interface ide3... ide3: Wait for ready failed before probe ! Probing IDE interface ide4... ide4: Wait for ready failed before probe ! Probing IDE interface ide5... ide5: Wait for ready failed before probe ! hda: ATAPI 40X DVD-ROM CD-R/RW drive, 2048kB Cache, UDMA(33) Uniform CD-ROM driver Revision: 3.20 mice: PS/2 mouse device common for all mice input: AT Translated Set 2 keyboard on isa0060/serio0 input: ImPS/2 Logitech Wheel Mouse on isa0060/serio1 NET: Registered protocol family 2 IP: routing cache hash table of 4096 buckets, 64Kbytes TCP: Hash tables configured (established 131072 bind 65536) Initializing IPsec netlink socket NET: Registered protocol family 1 NET: Registered protocol family 17 Starting balanced_irq ACPI: (supports S0 S1 S3 S4 S5) ACPI wakeup devices: VBTN PCI0 PCI1 PCI2 PCI3 PCI4 KBD USB0 USB1 USB2 USB3 Freeing unused kernel memory: 200k freed SCSI subsystem initialized libata version 1.02 loaded. ata_piix version 1.02 ACPI: PCI interrupt 0000:00:1f.2[C] -> GSI 20 (level, low) -> IRQ 20 PCI: Setting latency timer of device 0000:00:1f.2 to 64 ata1: SATA max UDMA/133 cmd 0xFE00 ctl 0xFE12 bmdma 0xFEA0 irq 20 ata2: SATA max UDMA/133 cmd 0xFE20 ctl 0xFE32 bmdma 0xFEA8 irq 20 ata1: dev 0 cfg 49:2f00 82:346b 83:7f01 84:4003 85:3469 86:3e01 87:4003 88:207f ata1: dev 0 ATA, max UDMA/133, 312581808 sectors: lba48 ata1: dev 0 configured for UDMA/133 scsi0 : ata_piix ATA: abnormal status 0xFF on port 0xFE27 ata2: disabling port scsi1 : ata_piix Vendor: ATA Model: ST3160023AS Rev: 8.05 Type: Direct-Access ANSI SCSI revision: 05 SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB) SCSI device sda: drive cache: write back sda: sda1 sda2 sda3 < sda5 sda6 sda7 > sda4 Attached scsi disk sda at scsi0, channel 0, id 0, lun 0 kjournald starting. Commit interval 5 seconds EXT3-fs: mounted filesystem with ordered data mode. ACPI: PCI interrupt 0000:03:00.0[A] -> GSI 16 (level, low) -> IRQ 16 hw_random: RNG not detected Linux agpgart interface v0.100 (c) Dave Jones agpgart: Detected an Intel 915G Chipset. agpgart: Maximum main memory to use for agp memory: 816M agpgart: AGP aperture is 256M @ 0x0 USB Universal Host Controller Interface driver v2.2 ACPI: PCI interrupt 0000:00:1d.0[A] -> GSI 21 (level, low) -> IRQ 21 uhci_hcd 0000:00:1d.0: Intel Corp. 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #1 PCI: Setting latency timer of device 0000:00:1d.0 to 64 uhci_hcd 0000:00:1d.0: irq 21, io base 0xff80 uhci_hcd 0000:00:1d.0: new USB bus registered, assigned bus number 1 hub 1-0:1.0: USB hub found hub 1-0:1.0: 2 ports detected ACPI: PCI interrupt 0000:00:1d.1[B] -> GSI 22 (level, low) -> IRQ 22 uhci_hcd 0000:00:1d.1: Intel Corp. 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #2 PCI: Setting latency timer of device 0000:00:1d.1 to 64 uhci_hcd 0000:00:1d.1: irq 22, io base 0xff60 uhci_hcd 0000:00:1d.1: new USB bus registered, assigned bus number 2 hub 2-0:1.0: USB hub found hub 2-0:1.0: 2 ports detected ACPI: PCI interrupt 0000:00:1d.2[C] -> GSI 18 (level, low) -> IRQ 18 uhci_hcd 0000:00:1d.2: Intel Corp. 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #3 PCI: Setting latency timer of device 0000:00:1d.2 to 64 uhci_hcd 0000:00:1d.2: irq 18, io base 0xff40 uhci_hcd 0000:00:1d.2: new USB bus registered, assigned bus number 3 hub 3-0:1.0: USB hub found hub 3-0:1.0: 2 ports detected ACPI: PCI interrupt 0000:00:1d.3[D] -> GSI 23 (level, low) -> IRQ 23 uhci_hcd 0000:00:1d.3: Intel Corp. 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #4 PCI: Setting latency timer of device 0000:00:1d.3 to 64 uhci_hcd 0000:00:1d.3: irq 23, io base 0xff20 uhci_hcd 0000:00:1d.3: new USB bus registered, assigned bus number 4 hub 4-0:1.0: USB hub found hub 4-0:1.0: 2 ports detected ohci1394: $Rev: 1223 $ Ben Collins ACPI: PCI interrupt 0000:03:00.2[B] -> GSI 17 (level, low) -> IRQ 17 ohci1394: fw-host0: OHCI-1394 1.1 (PCI): IRQ=[17] MMIO=[dfcfa800-dfcfafff] Max Packet=[2048] ieee1394: Host added: ID:BUS[0-00:1023] GUID[00023c041107fa77] ibm_acpi: ec object not found EXT3 FS on sda5, internal journal kjournald starting. Commit interval 5 seconds EXT3 FS on sda7, internal journal EXT3-fs: mounted filesystem with ordered data mode. Adding 1020088k swap on /dev/sda6. Priority:-1 extents:1 e100: eth0: e100_watchdog: link up, 100Mbps, full-duplex apm: BIOS version 1.2 Flags 0x03 (Driver version 1.16ac) apm: disabled - APM is not SMP safe. Unable to handle kernel paging request at virtual address f89e7b00 printing eip: c0187452 *pde = 37ff1067 *pte = 00000000 Oops: 0000 [#1] PREEMPT SMP Modules linked in: binfmt_misc video ohci1394 ieee1394 uhci_hcd intel_agp agpgart i2c_i801 i2c_core snd_emu10k1 snd_rawmidi snd_seq_device snd_ac97_codec snd_pcm snd_timer snd_page_alloc snd_util_mem snd_hwdep snd soundcore ext3 jbd ata_piix libata sd_mod scsi_mod CPU: 0 EIP: 0060:[] Not tainted VLI EFLAGS: 00010286 (2.6.10-rc1-mm3) EIP is at proc_get_inode+0xa0/0x184 eax: 00000000 ebx: f89e7b00 ecx: 00000001 edx: f7ee7000 esi: f62964bc edi: f66d6380 ebp: f7ee7de8 esp: f7ee7dc8 ds: 007b es: 007b ss: 0068 Process bash (pid: 5322, threadinfo=f7ee7000 task=f5d8c550) Stack: f62964bc f0000337 f7ee7de4 c02f3259 00000001 f66d6380 f4db2313 f66d63cf f7ee7e1c c018a0e6 f7f75200 f0000337 f66d6380 00000003 00000001 dead4ead ffffffea 00000000 fffffff4 f4db22a0 f5ea34bc f7ee7e3c c0169637 f5ea34bc Call Trace: [] show_stack+0x80/0x96 [] show_registers+0x161/0x1da [] die+0x107/0x190 [] do_page_fault+0x495/0x6cb [] error_code+0x2b/0x30 [] proc_lookup+0x7c/0xc4 [] real_lookup+0xab/0xc9 [] do_lookup+0x7d/0x88 [] link_path_walk+0x73e/0xef1 [] path_lookup+0x9a/0x163 [] __user_walk+0x2b/0x48 [] vfs_stat+0x1a/0x55 [] sys_stat64+0x19/0x38 [] sysenter_past_esp+0x52/0x71 Code: b7 47 0e 66 85 c0 74 06 0f b7 c0 89 46 2c 8b 5f 28 c7 45 f0 01 00 00 00 85 db 74 46 b8 01 00 00 00 e8 6a 54 f9 ff e8 9e 06 04 00 <83> 3b 02 0f 84 cf 00 00 00 c1 e0 07 01 d8 ff 80 00 01 00 00 b8 <6>note: bash[5322] exited with preempt_count 1 --Boundary-00=_Kf2jBe24bWJcf9j-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/