Messages in this thread | | | Subject | Re: [PATCH] powerpc/sysrq: Fix oops whem ppmu is not registered | From | Madhavan Srinivasan <> | Date | Tue, 19 Sep 2017 15:34:40 +0530 |
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On Tuesday 19 September 2017 03:30 PM, Michael Ellerman wrote: > Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> writes: > >> Kernel crashes if power pmu is not registered and user tries to dump >> regs with 'echo p > /proc/sysrq-trigger'. Sample log: >> >> Unable to handle kernel paging request for data at address 0x00000008 >> Faulting instruction address: 0xc0000000000d52f0 >> >> NIP [c0000000000d52f0] perf_event_print_debug+0x10/0x230 >> LR [c00000000058a938] sysrq_handle_showregs+0x38/0x50 >> Call Trace: >> printk+0x38/0x4c (unreliable) >> __handle_sysrq+0xe4/0x270 >> write_sysrq_trigger+0x64/0x80 >> proc_reg_write+0x80/0xd0 >> __vfs_write+0x40/0x200 >> vfs_write+0xc8/0x240 >> SyS_write+0x60/0x110 >> system_call+0x58/0x6c > Thanks. > > I added: > > Fixes: 5f6d0380c640 ("powerpc/perf: Define perf_event_print_debug() to print PMU register values") > > But I don't think I'll Cc stable, I can't think why we'd ever *not* have > a ppmu registered. How did you hit it? mpe,
We hit this in a compact mode setup where the distro kernel did not have the pmu support for the base pvr.
Maddy
> cheers >
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