On 02/12/2012 06:08 AM, Stephen Rothwell wrote: > Hi all, > > Just a quick note to say I got a boot OOPs with next-20120208 and 9 on a > Power7 blade (my other PowerPC boot tests are ok. I'll investigate this > further on Monday. > > The line referenced below is: > > BUG_ON(!kobj || !kobj->sd || !attr); > > in sysfs_create_file(). > > calling .topology_init+0x0/0x1ac @ 1 > initcall 7_.async_cpu_up+0x0/0x40 returned 0 after 9765 usecs > async_continuing @ 20 after 9765 usec > ------------[ cut here ]------------ > kernel BUG at fs/sysfs/file.c:573! > Oops: Exception in kernel mode, sig: 5 [#1] > SMP NR_CPUS=32 NUMA pSeries > Modules linked in: > NIP: c00000000024a35c LR: c0000000004ee050 CTR: c00000000083ca24 > REGS: c0000003fd9e7560 TRAP: 0700 Not tainted (3.3.0-rc2-autokern1) > MSR: 8000000000029032 <SF,EE,ME,IR,DR,RI> CR: 88002082 XER: 0000000f > CFAR: c00000000024a370 > TASK = c0000003fd9e8000[20] 'kworker/u:6' THREAD: c0000003fd9e4000 CPU: 0 > GPR00: 0000000000000001 c0000003fd9e77e0 c000000000d19bb8 0000000000000000 > GPR04: c000000000bf37a8 0000000000000008 8000000002096400 0000000000000000 > GPR08: 0000000000000000 c000000000f80028 c000000000d52bd8 0000000000000000 > GPR12: 0000000048002088 c00000000f33b000 0000000001affa78 00000000009aa000 > GPR16: 0000000000e1f3c8 0000000002d517f0 0000000001aff984 0000000000000060 > GPR20: 0000000000000000 ffffffffffffffff 0000000000000000 c000000000c45128 > GPR24: 0000000000000000 0000000000000008 0000000000000000 c000000000c44200 > GPR28: c000000000f80028 0000000000000008 c000000000c85038 0000000000000002 > NIP [c00000000024a35c] .sysfs_create_file+0x1c/0x40 > LR [c0000000004ee050] .device_create_file+0x20/0x40 > Call Trace: > [c0000003fd9e77e0] [c0000003fd9e78a0] 0xc0000003fd9e78a0 (unreliable) > [c0000003fd9e7850] [c00000000083c9a4] .register_cpu_online+0x1d0/0x250 > [c0000003fd9e7900] [c00000000083ca8c] .sysfs_cpu_notify+0x68/0x28c > [c0000003fd9e79b0] [c00000000083769c] .notifier_call_chain+0x9c/0x100 > [c0000003fd9e7a50] [c0000000000a5878] .__cpu_notify+0x38/0x80 > [c0000003fd9e7ad0] [c00000000083e124] ._cpu_up+0x10c/0x178 > [c0000003fd9e7b90] [c00000000083e2c8] .cpu_up+0x138/0x164 > [c0000003fd9e7c20] [c000000000ba46d0] .async_cpu_up+0x28/0x40 > [c0000003fd9e7ca0] [c0000000000d81ec] .async_run_entry_fn+0xbc/0x1f0 > [c0000003fd9e7d50] [c0000000000c7cbc] .process_one_work+0x19c/0x590 > [c0000003fd9e7e10] [c0000000000c8618] .worker_thread+0x188/0x4b0 > [c0000003fd9e7ed0] [c0000000000ce57c] .kthread+0xbc/0xd0 > [c0000003fd9e7f90] [c000000000021448] .kernel_thread+0x54/0x70 > Instruction dump: > 7fa3eb78 ebe1fff8 eba1ffe8 7c0803a6 4e800020 2c230000 41820024 e8630030 > 7c800074 7800d182 2fa30000 419e0014 <0b000000> 38a00002 4bfffebc e8630030 > ---[ end trace 31fd0ba7d8756001 ]--- > initcall .topology_init+0x0/0x1ac returned 0 after 0 usecs > calling .pcibios_init+0x0/0xe8 @ 1 > PCI: Probing PCI hardware > PCI: Probing PCI hardware done > initcall .pcibios_init+0x0/0xe8 returned 0 after 0 usecs > calling .add_system_ram_resources+0x0/0x140 @ 1 > initcall .add_system_ram_resources+0x0/0x140 returned 0 after 0 usecs > calling .__machine_initcall_powermac_pmac_i2c_create_platform_devices+0x0/0xc8 @ 1 > initcall .__machine_initcall_powermac_pmac_i2c_create_platform_devices+0x0/0xc8 returned 0 after 0 usecs > calling .opal_init+0x0/0x1cc @ 1 > opal: Node not found > initcall .opal_init+0x0/0x1cc returned -19 after 0 usecs > calling .__machine_initcall_pseries_ioei_init+0x0/0xa0 @ 1 > I took a brief look.. This looks like a race in register_cpu_online(). init/main.c: calls smp_init() followed by do_basic_setup(). do_basic_setup() executes all the post-smp initcalls. arch/powerpc/kernel/sysfs.c:topology_init() is a subsys_initcall. Hence it gets run from do_basic_setup(). And topology_init() does 2 things: It calls register_cpu_notifier() and also calls register_cpu_online() inside a 'for' loop. And the sysfs_cpu_notify() function also calls register_cpu_online(). This was safe as long as topology_init() and CPU hotplug were run serially, (ie., smp_init() finishing all cpu onlining and only then calling do_basic_setup(), as was done previous to Arjan's patch). But Arjan's patch makes these 2 things to run in parallel and since register_cpu_online() doesn't have any protection, we hit the race condition. I'll try to take a deeper look into this tomorrow... Regards, Srivatsa S. Bhat IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
