> > > I often wonder whether it's really a good idea to even allow the > > > unloading of patch modules at all. It adds complexity to the livepatch > > > code. Is it worth it? I don't have an answer but I'd be interested in > > > other people's opinion. > > > > I could imagine a situation when a livepatch causes, for example, > > performance, problems on a server because of the redirection > > to the new code. Then it might be handy to disable the patch > > and ftrace handlers completely. > > Fair enough, though it sounds theoretical. It would be good to know > we're supporting actual real world use cases. We distribute cumulative "replace_all" patches at SUSE. replace_all means that all previous patches are reverted in the process of application. All livepatch modules with zero refcount are removed. This keeps a number of loaded modules low and system's state well defined, which is always a good thing, because a customer might run into problems and we'd have to debug it. It is true that it is a limitation too. Especially for state changes and data structure modifications. Sometimes it is easy to patch a system, but impossible to unpatch it. Because we don't have a consistency on a state level, only on a task/process level. But I perceive this also as an advantage. I have to always know what a livepatch does exactly and I discovered couple of problems just because I had to think about unloading of modules. Miroslav -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
