| Message ID | 1505801826-12396-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 4917fcb58cc73f6b81455e3c5f960144809ddf1a |
| Headers | show |
| Series | powerpc/sysrq: Fix oops whem ppmu is not registered | expand |
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? cheers
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 >
On Tue, 2017-09-19 at 06:17:06 UTC, Ravi Bangoria wrote: > 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 > > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> > Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/4917fcb58cc73f6b81455e3c5f9601 cheers
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 2e3eb74..9e3da16 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -793,6 +793,11 @@ void perf_event_print_debug(void) u32 pmcs[MAX_HWEVENTS]; int i; + if (!ppmu) { + pr_info("Performance monitor hardware not registered.\n"); + return; + } + if (!ppmu->n_counter) return;