Messages in this thread | | | Subject | Re: LTTng finds abnormally long APIC interrupt handler : 58.2 ms | From | (Frank Ch. Eigler) | Date | Thu, 07 Aug 2008 14:15:57 -0400 |
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Steven Rostedt <rostedt@goodmis.org> writes:
> [...] >> It all holds in a small module. Having the ability to connect any marker >> on any generic probe from the lttng marker interface has been very >> useful to do all this. Actually, this module has to be built into the >> kernel because ftrace does not permit breeing the trace_ops data >> structure. :/ > > I did this purposely. The reason is that there is no safe way to release > the trace_ops, because you never know if something is in the function > you pointed to. If you remove the module after that, it crashes. > > I've been thinking of exporting it, and make it so that once you > register something to the trace_ops, I'll up the module count, and never > let that module unload.
This issue will need some sort of resolution if systemtap is to be able to hook up to ftrace. Perhaps we could have a second/nested API that suffers the costs of explicit reference counting, but does permit dynamic attach and robust detach.
- FChE
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