Hi - On Sat, Mar 21, 2009 at 05:04:22AM -0700, Andrew Morton wrote: > [...] > > There have been many mixed messages from LKML on the topic - sometimes > > mentioning systemtap is forbidden, other times necessary. Sorry about > > that. > > heh. We all love systemtap and want it to get better.
Great! > [...] > I have strong memories of being traumatised by reading the uprobes > code. What's the story on all of that nowadays? uprobes, being a layer upon utrace that provides a kprobes-like breakpointing API for user threads, is being refactored into several parts. I don't know about the aesthetics of it all, but I believe the general future plan is this: One piece would perform machine code analysis (to classify instructions for ideal/safe placement of breakpoints or for code patching), and another thin layer that uses this and utrace to manage user-space breakpoints. (Systemtap would interface at this point.) Then a user-space syscallish interface could come along to expose this to a super-ptrace client (to speed up gdb; perhaps to allow multiple debuggers). Plus one might as well add an ftrace-engine for it (directly analogous to the recent kprobe-based one that ftrace people found "cool".) > > > Actually it seems that the whole utrace-ftrace thing is a big > > > distraction and could/should just be omitted. This is a systemtap > > > feature and should be viewed as such. [...] > > > > utrace is a better way to perform user thread management than what is > > there now, and the utrace-ftrace widget shows how to *hook* thread > > events such as syscalls in a lighter weight / more managed way than > > the first one proposed. (That's one reason we've been participating > > in the ftrace discussions.) Of course it can be made to use the fine > > syscall pretty-printing code recently added. > > eh. Boring. Let's fix systemtap? There are several constituencies here, some of which find the above exciting. That's OK and we'd like to help them too. - FChE
