I tried booting 2.6.30-rc7 on my old '486, but it fails miserably during libata/pata_legacy's device scan: Linux version 2.6.30-rc7 (mikpe@brewer) (gcc version 4.3.4 20090517 (prerelease) (GCC) ) #1 Sun May 24 16:05:18 CEST 2009 KERNEL supported cpus: Intel GenuineIntel BIOS-provided physical RAM map: BIOS-88: 0000000000000000 - 000000000009f000 (usable) BIOS-88: 0000000000100000 - 0000000001c00000 (usable) last_pfn = 0x1c00 max_arch_pfn = 0x100000 init_memory_mapping: 0000000000000000-0000000001c00000 RAMDISK: 01abb000 - 01bef86b 28MB LOWMEM available. mapped low ram: 0 - 01c00000 low ram: 0 - 01c00000 node 0 low ram: 00000000 - 01c00000 node 0 bootmap 00001000 - 00001380 (7 early reservations) ==> bootmem [0000000000 - 0001c00000] #0 [0000000000 - 0000001000] BIOS data page ==> [0000000000 - 0000001000] #1 [0000100000 - 000031d1ec] TEXT DATA BSS ==> [0000100000 - 000031d1ec] #2 [0001abb000 - 0001bef86b] RAMDISK ==> [0001abb000 - 0001bef86b] #3 [000009f000 - 0000100000] BIOS reserved ==> [000009f000 - 0000100000] #4 [000031e000 - 0000320000] BRK ==> [000031e000 - 0000320000] #5 [0000007000 - 000000c000] PGTABLE ==> [0000007000 - 000000c000] #6 [0000001000 - 0000002000] BOOTMAP ==> [0000001000 - 0000002000] Zone PFN ranges: DMA 0x00000000 -> 0x00001000 Normal 0x00001000 -> 0x00001c00 Movable zone start PFN for each node early_node_map[2] active PFN ranges 0: 0x00000000 -> 0x0000009f 0: 0x00000100 -> 0x00001c00 Allocating PCI resources starting at 10000000 (gap: 1c00000:fe400000) Built 1 zonelists in Zone order, mobility grouping on. Total pages: 7015 Kernel command line: ro root=LABEL=/ console=ttyS1,115200 Initializing CPU#0 NR_IRQS:16 PID hash table entries: 128 (order: 7, 512 bytes) Console: colour VGA+ 80x25 console [ttyS1] enabled Dentry cache hash table entries: 4096 (order: 2, 16384 bytes) Inode-cache hash table entries: 2048 (order: 1, 8192 bytes) Memory: 24592k/28672k available (1467k kernel code, 3688k reserved, 465k data, 132k init, 0k highmem) virtual kernel memory layout: fixmap : 0xfffeb000 - 0xfffff000 ( 80 kB) vmalloc : 0xc2400000 - 0xfffe9000 ( 987 MB) lowmem : 0xc0000000 - 0xc1c00000 ( 28 MB) .init : 0xc02e6000 - 0xc0307000 ( 132 kB) .data : 0xc026eef0 - 0xc02e34f8 ( 465 kB) .text : 0xc0100000 - 0xc026eef0 (1467 kB) Checking if this processor honours the WP bit even in supervisor mode...Ok. Calibrating delay loop... 49.66 BogoMIPS (lpj=248320) Mount-cache hash table entries: 512 CPU: Intel 486 DX/4 stepping 00 Checking 'hlt' instruction... OK. net_namespace: 296 bytes NET: Registered protocol family 16 bio: create slab <bio-0> at 0 SCSI subsystem initialized NET: Registered protocol family 2 IP route cache hash table entries: 1024 (order: 0, 4096 bytes) TCP established hash table entries: 1024 (order: 1, 8192 bytes) TCP bind hash table entries: 1024 (order: 0, 4096 bytes) TCP: Hash tables configured (established 1024 bind 1024) TCP reno registered NET: Registered protocol family 1 Unpacking initramfs... Freeing initrd memory: 1234k freed platform rtc_cmos: registered platform RTC device (no PNP device found) msgmni has been set to 50 io scheduler noop registered io scheduler anticipatory registered (default) io scheduler deadline registered io scheduler cfq registered Real Time Clock Driver v1.12b Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A Driver 'sd' needs updating - please use bus_type methods scsi0 : pata_legacy ata1: PATA max PIO4 cmd 0x1f0 ctl 0x3f6 irq 14 ------------[ cut here ]------------ WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90() Modules linked in: Pid: 1, comm: swapper Not tainted 2.6.30-rc7 #1 Call Trace: [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01139b5>] ? warn_slowpath_common+0x45/0x80 [<c01139fa>] ? warn_slowpath_null+0xa/0x10 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c02f40e0>] ? legacy_init+0x44e/0x87f [<c02f3c92>] ? legacy_init+0x0/0x87f [<c0101021>] ? _stext+0x21/0x140 [<c01890ff>] ? proc_register+0x2f/0x190 [<c018938c>] ? create_proc_entry+0x5c/0xc0 [<c0135ebe>] ? register_irq_proc+0x6e/0x90 [<c02e6484>] ? kernel_init+0x6e/0xbf [<c02e6416>] ? kernel_init+0x0/0xbf [<c01031d7>] ? kernel_thread_helper+0x7/0x10 ---[ end trace ef1ee36e873ae3a0 ]--- scsi1 : pata_legacy ata2: PATA max PIO4 cmd 0x170 ctl 0x376 irq 15 ------------[ cut here ]------------ WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90() Modules linked in: Pid: 1, comm: swapper Tainted: G W 2.6.30-rc7 #1 Call Trace: [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01139b5>] ? warn_slowpath_common+0x45/0x80 [<c01139fa>] ? warn_slowpath_null+0xa/0x10 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c02f40e0>] ? legacy_init+0x44e/0x87f [<c02f3c92>] ? legacy_init+0x0/0x87f [<c0101021>] ? _stext+0x21/0x140 [<c01890ff>] ? proc_register+0x2f/0x190 [<c018938c>] ? create_proc_entry+0x5c/0xc0 [<c0135ebe>] ? register_irq_proc+0x6e/0x90 [<c02e6484>] ? kernel_init+0x6e/0xbf [<c02e6416>] ? kernel_init+0x0/0xbf [<c01031d7>] ? kernel_thread_helper+0x7/0x10 ---[ end trace ef1ee36e873ae3a1 ]--- scsi2 : pata_legacy ata3: PATA max PIO4 cmd 0x1e8 ctl 0x3ee irq 11 ------------[ cut here ]------------ WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90() Modules linked in: Pid: 1, comm: swapper Tainted: G W 2.6.30-rc7 #1 Call Trace: [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01139b5>] ? warn_slowpath_common+0x45/0x80 [<c01139fa>] ? warn_slowpath_null+0xa/0x10 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c02f40e0>] ? legacy_init+0x44e/0x87f [<c02f3c92>] ? legacy_init+0x0/0x87f [<c0101021>] ? _stext+0x21/0x140 [<c01890ff>] ? proc_register+0x2f/0x190 [<c018938c>] ? create_proc_entry+0x5c/0xc0 [<c0135ebe>] ? register_irq_proc+0x6e/0x90 [<c02e6484>] ? kernel_init+0x6e/0xbf [<c02e6416>] ? kernel_init+0x0/0xbf [<c01031d7>] ? kernel_thread_helper+0x7/0x10 ---[ end trace ef1ee36e873ae3a2 ]--- scsi3 : pata_legacy ata4: PATA max PIO4 cmd 0x168 ctl 0x36e irq 10 ------------[ cut here ]------------ WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90() Modules linked in: Pid: 1, comm: swapper Tainted: G W 2.6.30-rc7 #1 Call Trace: [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01139b5>] ? warn_slowpath_common+0x45/0x80 [<c01139fa>] ? warn_slowpath_null+0xa/0x10 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c02f40e0>] ? legacy_init+0x44e/0x87f [<c02f3c92>] ? legacy_init+0x0/0x87f [<c0101021>] ? _stext+0x21/0x140 [<c01890ff>] ? proc_register+0x2f/0x190 [<c018938c>] ? create_proc_entry+0x5c/0xc0 [<c0135ebe>] ? register_irq_proc+0x6e/0x90 [<c02e6484>] ? kernel_init+0x6e/0xbf [<c02e6416>] ? kernel_init+0x0/0xbf [<c01031d7>] ? kernel_thread_helper+0x7/0x10 ---[ end trace ef1ee36e873ae3a3 ]--- scsi4 : pata_legacy ata5: PATA max PIO4 cmd 0x160 ctl 0x366 irq 12 ------------[ cut here ]------------ WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90() Modules linked in: Pid: 1, comm: swapper Tainted: G W 2.6.30-rc7 #1 Call Trace: [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c01139b5>] ? warn_slowpath_common+0x45/0x80 [<c01139fa>] ? warn_slowpath_null+0xa/0x10 [<c01fbb05>] ? ata_host_detach+0x75/0x90 [<c02f40e0>] ? legacy_init+0x44e/0x87f [<c02f3c92>] ? legacy_init+0x0/0x87f [<c0101021>] ? _stext+0x21/0x140 [<c01890ff>] ? proc_register+0x2f/0x190 [<c018938c>] ? create_proc_entry+0x5c/0xc0 [<c0135ebe>] ? register_irq_proc+0x6e/0x90 [<c02e6484>] ? kernel_init+0x6e/0xbf [<c02e6416>] ? kernel_init+0x0/0xbf [<c01031d7>] ? kernel_thread_helper+0x7/0x10 ---[ end trace ef1ee36e873ae3a4 ]--- serio: i8042 KBD port at 0x60,0x64 irq 1 serio: i8042 AUX port at 0x60,0x64 irq 12 mice: PS/2 mouse device common for all mice input: PC Speaker as /class/input/input0 TCP cubic registered input: AT Translated Set 2 keyboard as /class/input/input1 At this point the kernel hangs until I flip the power switch. This is 100% reproducible. 2.6.29 worked Ok. A bug hunt showed that 2.6.29-git3 was the last kernel to boot Ok on this machine, and every single one since 2.6.29-git4 hang. 2.6.29-git4 was when Arjan removed the "async is off by default" code, in commit 9710794383ee5008d67f1a6613a4717bf6de47bc. Reverting that from 2.6.30-rc7 gives me a working kernel again. I haven't had any async problems on my other machines, so presumably the bug is in pata_legacy, or due to the machine being so insanely slow. (I just saw James Bottomley's "[PATCH] async: make sure independent async domains can't accidentally entangle". Unfortunately that patch makes no difference to this machine's async-related boot failure.) /Mikael -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html