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    SubjectRe: sparc boot failure due to perf init
    On Fri, Jan 07, 2011 at 09:18:05PM +0100, Sam Ravnborg wrote:
    > I have upgraded my Sun Blade 100 to latest mainline,
    > and when it booted I hit an oops.
    >
    > Relevant bits from the oops:
    > Mount-cache hash table entries: 512
    > Performance events: perf (null) <<<<<<<<<<<<<<<<<<<
    > Unable to handle kernel NULL pointer dereference
    > tsk->{mm,active_mm}->context = 0000000000000000
    > tsk->{mm,active_mm}->pgd = fffff800003e4634
    > \|/ ____ \|/
    > "@'/ .. \`@"
    > /_| \__/ |_\
    > \__U_/
    > swapper(1): Oops [#1]
    > TSTATE: 0000004480001606 TPC: 000000000055c180 TNPC: 000000000055c184 Y: 00000000 Not tainted
    > TPC: <strcmp+0x0/0x40>
    > g0: fffff8000f03f800 g1: 00000000007df800 g2: 000000000078f918 g3: 0000000000799168
    > g4: fffff8000f0358c0 g5: fffff80000c22000 g6: fffff8000f038000 g7: 0000000000000001
    > o0: 0000000000000000 o1: 000000000073b050 o2: 0000000000000001 o3: 0000000000000001
    > o4: fffff8000f0356c8 o5: 0000000000000000 sp: fffff8000f03b531 ret_pc: 00000000007b9e30
    > RPC: <init_hw_perf_events+0x30/0x168>
    > l0: 0000000000000000 l1: 00000000007e0a80 l2: 00000000007e2140 l3: 0000000000000001
    > l4: 0000000000000000 l5: 0000000000000000 l6: 0000000000000000 l7: 0000000000777b78
    > i0: fffff80001402a80 i1: 0000000000000000 i2: 0000000000000001 i3: 0000000000000001
    > i4: 0000000000000000 i5: 0000000000000005 i6: fffff8000f03b5e1 i7: 00000000007b41c8
    > I7: <do_one_initcall+0x68/0x140>
    >
    > The line mared "<<<<<<<<<<<<<" is added by my printf debugging.
    > It shows that sparc_pmu_type is NULL.
    >
    > sparc_pmu_type is set in cpu_type_probe(void) which is:
    >
    > arch_initcall(cpu_type_probe);
    >
    > But init_hw_perf_events() is:
    >
    > early_initcall(init_hw_perf_events);
    >
    > So we end up calling init_hw_perf_events() before we call cpu_type_probe(),
    > and sparc_pmu_type is not set.
    >
    > This was introduced by:
    > "perf, arch: Cleanup perf-pmu init vs lockup-detector" - 004417a6d468e24399e383645c068b498eed84ad
    Note: I did not try a revert or anything.
    I just looked at the patch and concluded this was the culprint.

    Sam


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