Messages in this thread | | | Date | Tue, 29 Jul 2008 19:19:35 -0400 | From | Mathieu Desnoyers <> | Subject | Re: module-placed markers/tracepoints |
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* Frank Ch. Eigler (fche@redhat.com) wrote: > Hi - > > On Tue, Jul 29, 2008 at 06:41:16PM -0400, Mathieu Desnoyers wrote: > > > Some locals are wondering -- is there code for (or need for new code > > > for) incrementing module reference counts while markers and/or > > > tracepoints resident in modules have active clients? > > > > Probe module unloading is supposed to be done automatically assuming the > > following module unload behavior [...] > > The question was more that if module-placed markers/tracepoints are > armed, is there any mechanism to prevent the modules' unloading. For > kprobes, there is. > > - FChE
I see, it's the other way around : declaring a marker/tracepoint in a module.
When you register to a marker/tracepoint, you actually register the probe in a hash table. It will be connected to every placed marker/tracepoint with that given name. Upon module load, markers/tp that match the name are connected, and upon module unload all markers/tp are simply freed by module.c : unlike kprobes, there is no need for the marker/tp infrastructures to keep track of every marker/tp. So we don't need any refcount on the module which has the marker/tp.
However, the probe question is important; I think a synchronize_sched() is missing to handle unload of marker/tp probes modules.
Mathieu
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