Between 2.6.33 and 2.6.34 the PMU code was made modular. The x86_pmu_enable() call was extended to disable cpuc->enabled and iterate the counters, enabling one at a time, before calling enable_all() at the end, followed by re-enabling cpuc->enabled.
Since cpuc->enabled was set to 0, that change effectively caused the "val |= ARCH_PERFMON_EVENTSEL_ENABLE;" code in p6_pmu_enable_event() and p6_pmu_disable_event() to be dead code that was never called. This change removes this code (which was confusing) and adds some extra commentary to make it more clear what is going on. Signed-off-by: Vince Weaver <[email protected]> diff -ur linux-3.7-rc1.orig/arch/x86/kernel/cpu/perf_event_p6.c linux-3.7-rc1/arch/x86/kernel/cpu/perf_event_p6.c --- linux-3.7-rc1.orig/arch/x86/kernel/cpu/perf_event_p6.c 2012-10-14 17:41:04.000000000 -0400 +++ linux-3.7-rc1/arch/x86/kernel/cpu/perf_event_p6.c 2012-10-19 15:58:50.416238172 -0400 @@ -64,25 +64,25 @@ static inline void p6_pmu_disable_event(struct perf_event *event) { - struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); struct hw_perf_event *hwc = &event->hw; u64 val = P6_NOP_EVENT; - if (cpuc->enabled) - val |= ARCH_PERFMON_EVENTSEL_ENABLE; - (void)wrmsrl_safe(hwc->config_base, val); } static void p6_pmu_enable_event(struct perf_event *event) { - struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); struct hw_perf_event *hwc = &event->hw; u64 val; val = hwc->config; - if (cpuc->enabled) - val |= ARCH_PERFMON_EVENTSEL_ENABLE; + + /* + * p6 only has a global event enable, set on PerfEvtSel0 + * We "disable" events by programming P6_NOP_EVENT + * and we rely on p6_pmu_enable_all() being called + * to actually enable the events. + */ (void)wrmsrl_safe(hwc->config_base, val); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
