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    Subject[tip:perf/core] x86, perf: Unmask LVTPC only if we have APIC supported
    Commit-ID:  8576e1971663ffdb6139041de97cdd2e1d4791cc
    Gitweb: http://git.kernel.org/tip/8576e1971663ffdb6139041de97cdd2e1d4791cc
    Author: Cyrill Gorcunov <gorcunov@openvz.org>
    AuthorDate: Sat, 13 Mar 2010 11:11:16 +0300
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Sat, 13 Mar 2010 13:32:27 +0100

    x86, perf: Unmask LVTPC only if we have APIC supported

    Ingo reported:

    |
    | There's a build failure on -tip with the P4 driver, on UP 32-bit, if
    | PERF_EVENTS is enabled but UP_APIC is disabled:
    |
    | arch/x86/built-in.o: In function `p4_pmu_handle_irq':
    | perf_event.c:(.text+0xa756): undefined reference to `apic'
    | perf_event.c:(.text+0xa76e): undefined reference to `apic'
    |

    So we have to unmask LVTPC only if we're configured to have one.

    Reported-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
    CC: Lin Ming <ming.m.lin@intel.com>
    CC: Peter Zijlstra <peterz@infradead.org>
    LKML-Reference: <20100313081116.GA5179@lenovo>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    arch/x86/kernel/cpu/perf_event_p4.c | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
    index 381f593..ef861da 100644
    --- a/arch/x86/kernel/cpu/perf_event_p4.c
    +++ b/arch/x86/kernel/cpu/perf_event_p4.c
    @@ -365,8 +365,10 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
    }

    if (handled) {
    +#ifdef CONFIG_X86_LOCAL_APIC
    /* p4 quirk: unmask it again */
    apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
    +#endif
    inc_irq_stat(apic_perf_irqs);
    }


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