On Tue, 29 Apr 2014, Peter Zijlstra wrote: > On Mon, Apr 28, 2014 at 10:21:34AM -0400, Vince Weaver wrote: > > so it's looking more and more like this issue is with a > > PERF_COUNT_SW_TASK_CLOCK > > event. > > But they don't actually use the hlist thing..
yes. This turns out into another issue that I think is just use-after-free memory corruption exhibiting itself a different way. I've documented at least 8 different types of error message that I think are all due to this issue. > So this is a different problem from the hlist corruption? Who knows. That's why I'm trying to get this issue fixed so I can figure out which of the 10+ other bugs I'm tracking are the same or different. > > This is made all the more confusing because the PERF_COUNT_SW_TASK_CLOCK > > events are handled by their own PMU even though it's faked up so they look > > like regular software events. Is there a reason for that? > > This was the easiest route when we introduced the mulitple pmu thing or > so, its been on the todo list for a cleanup ever since :-/ It was very confusing and poorly documented, as is much of the perf_event files. And yes, I know, I should do something about it rather than complain. I've actually given up on source code inspection to figure out what's going on in kernel/events/core.c. What I do now is write simple test cases and do an ftrace function trace. The results are often surprising. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/