* Bill Trost ([email protected]) wrote: > Hi, > > I'm trying to investigate a problem under Linux 2.6.39.4 involving > kworker threads and am pretty much stymied. I've tried enabling > various events using --function and --probe and it's been > very hit or miss. Very often, "lttng enable-event" comes back > with nothing more specific than "bad ioctl", but every once > in a while I'll find a symbol I can add a probe point for. > > So: What does "--probe" mean?
--probe allows to put a kprobe (breakpoint) at a kernel text address or symbol. > What does "--function" mean, --function allows to put a kretprobes at a function entry site (using its symbol name), which will trigger events at function entry return. > and how does > it differ from "--probe"? How do I determine what symbols are valid for > each of these options? It entirely depends on which functions are blacklisted in the kernel (this is an attribute added to the functions specifically for kprobes). The keyword is "__kprobes". > And, maybe as a worked example, how do I > trace what work is being enqueued and run by the kworker threads? For this level of details, I think kprobes/kretprobes will not currently allow you to fetch it. The two options we have are: - use static tracepoints. Is there a tracepoint that targets the information you are looking for ? Try "lttng list -k". - or extend the dynamic probing to allow fetching variables from debug information, Thanks, Mathieu > > Thanks, > Bill > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
