Messages in this thread | | | Date | Mon, 20 Dec 2021 10:54:55 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3] perf/core: Set event shadow time for inactive events too |
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On Mon, Dec 20, 2021 at 10:30:34AM +0100, Peter Zijlstra wrote: > On Sat, Dec 18, 2021 at 09:09:05AM +0000, Song Liu wrote:
> > Unfortunately, this change bring the bug back. For time_enabled in rdpmc > > case to work properly, we have to touch all the enabled but not running > > events, right? > > Ohh.. argh. I think I see why, it looses the context time enable edge, > and because this is all strictly per-event in the uapi (there is no ctx > representation) it can't be cured by improving ctx time handling :/ > > Bah, I so hate this.
For now I've added this then ...
+/* + * Because the userpage is strictly per-event (there is no concept of context, + * so there cannot be a context indirection), every userpage must be updated + * when context time starts :-( + * + * IOW, we must not miss EVENT_TIME edges. + */ static inline bool event_update_userpage(struct perf_event *event)
But that same is not true for perf_event_read_local(), that *has* access to the context and so must be able to DTRT.
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