I've been looking at usage of per-CPU variable cpu_hw_events in arch/powerpc/perf/core-book3s.c.
power_pmu_enable() and power_pmu_disable() (pmu::pmu_enable() and pmu::pmu_disable()) are accessing the variable and the callbacks are invoked always with disabled interrupts. power_pmu_event_init() (pmu::event_init()) is invoked from preemptible context and uses get_cpu_var() to obtain a stable pointer (by disabling preemption). pmu::pmu_enable() and pmu::pmu_disable() can be invoked via a hrtimer (perf_mux_hrtimer_handler()) and it invokes pmu::pmu_enable() and pmu::pmu_disable() as part of the callback. Is there anything that prevents the timer callback to interrupt pmu::event_init() while it is accessing per-CPU data? Sebastian
