[PATCH v3 1/5] hw_breakpoint: Add step_needed event attribute
From: peterz@infradead.org (Peter Zijlstra)
Date: 2017-08-01 08:18:31
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On Mon, Jul 31, 2017 at 04:10:29PM +0530, Pratyush Anand wrote:
quoted hunk ↗ jump to hunk
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 24a635887f28..7da951f94b47 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h@@ -233,6 +233,12 @@ struct hw_perf_event { */ u64 freq_time_stamp; u64 freq_count_stamp; + /* + * A HW breakpoint user can either have it's own step handling + * mechanism or it can use default step handling meachanism defined + * by arch code. Set step_needed to use default mechanism. + */ + int step_needed;
You'll note that there is an anonymous structure inside the anonymous union specifically dedicated to hardware breakpoint state. Why not put it there?
quoted hunk ↗ jump to hunk
#endif };diff --git a/kernel/events/core.c b/kernel/events/core.c index 6c4e523dc1e2..66ce5574e778 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c@@ -9444,9 +9444,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, } else if (is_write_backward(event)){ event->overflow_handler = perf_event_output_backward; event->overflow_handler_context = NULL; + event->hw.step_needed = 1; } else { event->overflow_handler = perf_event_output_forward; event->overflow_handler_context = NULL; + event->hw.step_needed = 1; }
These here need a comment, because even if I'd know now why the heck we need that = 1 here, I'd sure as hell won't know tomorrow.