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Re: Re: systemtap 2.2.1 installcheck => kernel BUG at .. kprobes.c:707
- From: "Frank Ch. Eigler" <fche at redhat dot com>
- To: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- Cc: Timo Juhani Lindfors <timo dot lindfors at iki dot fi>, systemtap at sourceware dot org, srostedt at redhat dot com, "yrl dot pp-manager dot tt at hitachi dot com" <yrl dot pp-manager dot tt at hitachi dot com>
- Date: Wed, 22 May 2013 10:21:49 -0400
- Subject: Re: Re: systemtap 2.2.1 installcheck => kernel BUG at .. kprobes.c:707
- References: <84obc93lq6 dot fsf at sauna dot l dot org> <y0m61yhn6ff dot fsf at fche dot csb> <519ADFB6 dot 9090409 at hitachi dot com>
Hi, Masami -
> I've found the root cause of this bug at last.
Thanks for looking into it!
> [...]
> This shouldn't happen if the probe unregistration is done AFTER
> kprobes_module_callback is called (because at that time the op
> is gone), and kprobe-tracer does it.
> So, ftrace never gets this bug, but systemtap does.
I don't quite understand. In systemtap, as per runtime/transport/transport.c,
we use a notifier priority of 1 for the _stp_module_notifier, so that we get
notified after the kprobes_module_callback. I believe this behavior matches
ftrace.
- FChE