Hi Thomas, > Looks like the old ghosts of exit race conditions have come back to > haunt us. > > I have no idea how this can happen because all protections are in > place. Can you try to reproduce that with function tracing enabled? > > If the machine is still accessible you can retrieve the trace in the > usual way. Otherwise you need to enable ftrace_dump_on_oops and let it > spill out over the serial console. I have been able to catch this BUG again on a different PC during a reboot. Unfortunately, it happened before I had enabled ftrace_dump_on_oops. BTW: Is it possible to configure the tracing to be already active on boot? [ 4.844585] BUG: unable to handle kernel NULL pointer dereference at 0000001c [ 4.844598] IP: [<c107fb62>] __try_to_take_rt_mutex+0x52/0x100 [ 4.844599] *pde = 00000000 [ 4.844600] Oops: 0000 [#1] PREEMPT SMP [ 4.844620] Modules linked in: dis_irm(O+) es53xx(O) nfsd nfs lockd grace sunrpc bridge stp llc e100 mii e1000 kvm_intel kvm pcspkr psmouse i2c_i801 radeon drm_kms_helper ttm drm agpgart e1000e igb i2c_algo_bit i2c_core ixgbe mdio ptp pps_core dca parport_pc parport video backlight acpi_cpufreq processor coretemp autofs4 reiserfs microcode sg sd_mod ahci libahci ehci_pci ehci_hcd fan thermal_sys hwmon xhci_pci xhci_hcd [ 4.844621] CPU: 0 PID: 2392 Comm: ps Tainted: G O 3.18.13-rt10-2 #1 [ 4.844622] Hardware name: LENOVO 32282Z8/MAHOBAY, BIOS 9SKT70AUS 06/07/2013 [ 4.844622] task: ea3d0000 ti: ea3cc000 task.ti: ea3cc000 [ 4.844623] EIP: 0060:[<c107fb62>] EFLAGS: 00010282 CPU: 0 [ 4.844624] EIP is at __try_to_take_rt_mutex+0x52/0x100 [ 4.844625] EAX: 00000000 EBX: 00000000 ECX: ea3cdda8 EDX: 00000000 [ 4.844625] ESI: ea3d0000 EDI: ea072f04 EBP: ea3cdd88 ESP: ea3cdd78 [ 4.844625] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 [ 4.844626] CR0: 80050033 CR2: 0000001c CR3: 2aff3000 CR4: 001407d0 [ 4.844626] Stack: [ 4.844628] ea3d0000 ea072f04 ea3d04b0 ea3cdda8 ea3cdddc c1404169 00000001 ea3cdfec [ 4.844629] ea274201 ea3d0000 ea3d04b0 ea3d0000 00000001 00000000 00000000 ea3cddb4 [ 4.844630] 00000000 00000000 ea3d0000 ea072f04 c1045b01 00000078 ea3d0000 ea274800 [ 4.844630] Call Trace: [ 4.844633] [<c1404169>] rt_spin_lock_slowlock+0xf9/0x240 [ 4.844635] [<c1045b01>] ? pin_current_cpu+0x31/0x1a0 [ 4.844637] [<c1405567>] rt_spin_lock+0x27/0x30 [ 4.844638] [<c1051508>] __lock_task_sighand+0x38/0x70 [ 4.844640] [<c1196662>] do_task_stat+0xf2/0xd40 [ 4.844642] [<c1069580>] ? migrate_enable+0x80/0x180 [ 4.844644] [<c11f77ac>] ? lockref_put_or_lock+0x2c/0x40 [ 4.844646] [<c1201bd2>] ? debug_smp_processor_id+0x12/0x20 [ 4.844647] [<c1045c83>] ? unpin_current_cpu+0x13/0x60 [ 4.844647] [<c1069580>] ? migrate_enable+0x80/0x180 [ 4.844648] [<c11f77ac>] ? lockref_put_or_lock+0x2c/0x40 [ 4.844650] [<c115f9f5>] ? mntput_no_expire+0x25/0x150 [ 4.844651] [<c115fb40>] ? mntput+0x20/0x40 [ 4.844653] [<c1150220>] ? path_openat+0x120/0x550 [ 4.844654] [<c1068fab>] ? get_parent_ip+0xb/0x40 [ 4.844655] [<c11979bf>] proc_tgid_stat+0x1f/0x30 [ 4.844656] [<c1193312>] proc_single_show+0x42/0x80 [ 4.844657] [<c1163d12>] seq_read+0x82/0x380 [ 4.844658] [<c1150a3d>] ? final_putname+0x1d/0x40 [ 4.844659] [<c1163c90>] ? seq_lseek+0x1c0/0x1c0 [ 4.844660] [<c1142684>] vfs_read+0x74/0x140 [ 4.844661] [<c1142ca6>] SyS_read+0x46/0x90 [ 4.844662] [<c1405c54>] sysenter_do_call+0x12/0x12 [ 4.844669] Code: 83 cb 01 f0 0f b1 1e 39 d0 75 ee 8b 5f 0c 31 c0 83 e3 fe 74 0c 83 c4 04 5b 5e 5f 5d c3 8d 74 26 00 8b 75 f0 85 c9 74 1d 8b 57 08 <3b> 7a 1c 0f 85 93 00 00 00 89 d8 39 d1 75 db 89 ca 89 f8 e8 c6 [ 4.844671] EIP: [<c107fb62>] __try_to_take_rt_mutex+0x52/0x100 SS:ESP 0068:ea3cdd78 [ 4.844671] CR2: 000000000000001c [ 5.168516] ---[ end trace 0000000000000002 ]--- [ 5.168517] note: ps[2392] exited with preempt_count 1 [ 5.168554] ------------[ cut here ]- Regards Mathias -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
