WRT rwlocks. We actually cap reader count to 1 in PREEMPT_RT for that very reason. This is unfortunate, and one of the causes for performance degradation on -rt for certain workloads. There was some discussion during the rt-summit in Dresden about making kernel rwlocks non-pi-aware for this reason. Some more investigation is needed before we make a decision there.
Posted Oct 6, 2009 15:37 UTC (Tue) by simlo (subscriber, #10866)
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As I said: You could leave half-PI-aware : Let readers boost the writer, but not the other way around. This will most likely work in many cases. It means a RT task can't write-lock a rwlock must defer the operation to another task. Config options are needed....