Re: [PATCH v6 3/4] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter
From: Peter Zijlstra <peterz@infradead.org>
Date: 2015-08-05 13:59:37
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On Wed, Aug 05, 2015 at 03:53:17PM +0200, Peter Zijlstra wrote:
+/*
+ * NMI-safe method to read a local event, that is an event that
+ * is:
+ * - either for the current task, or for this CPU
+ * - does not have inherit set, for inherited task events
+ * will not be local and we cannot read them atomically
+ * - must not have a pmu::count method
+ */
+u64 perf_event_read_local(struct perf_event *event)
+{
+ unsigned long flags;
+ u64 val;
+
+ /*
+ * Disabling interrupts avoids all counter scheduling (context
+ * switches, timer based rotation and IPIs).
+ */
+ local_irq_safe(flags);Hmm, I think local_irq_save(flags) will compile much better. Obviously this patch hasn't seen a compiler up close.