On Fri, 2013-06-14 at 00:31 +1000, Michael Ellerman wrote: > On Thu, 2013-06-13 at 08:45 -0400, Steven Rostedt wrote: > > On Thu, 2013-06-13 at 21:04 +1000, Michael Ellerman wrote: > > > > > Although that should be sufficient to fix the bug, we also mark the > > > runlatch routines as notrace. They are called very early in the > > > exception entry and we are asking for trouble tracing them. They are > > > also fairly uninteresting and tracing them just adds unnecessary > > > overhead. > > > > Note, I usually lean towards tracing everything that can be traced, and > > only adding notrace to things that will actually cause a crash. If you > > don't like them to be traced, you can always do: > > Yeah fair enough. In this case I think we don't want to trace it. > Although it doesn't cause a crash right now (at least after part 1 of > this patch), it's being called at a time when things are fragile, and > it's possible we could get bitten again some other way if the > surrounding code changes. >
I wont push to trace it, as if it is fragile code, then it's best not to risk it. Tracing is always a second class citizen in the kernel ;-) > > > echo '*__ppc64_runlatch_*' > > > /sys/kernel/debug/tracing/set_ftrace_notrace > > > > and that will keep them from being traced. You can also add it to the > > kernel command line with: ftrace_notrace=*__ppc64_runlatch_* which will > > also disable them on boot up. > > > > Also trace-cmd has: > > > > trace-cmd record -p function_graph -n '*__ppc64_runlatch_*' > > > > that will do the same thing. > > > > Hmm, I should add a way to disable things that are usually considered > > noise. Perhaps add something like: > > > > > > FTRACE_DEFAULT_OFF(__ppc64_runlatch_on); > > > > That adds the function to a different section that places it into > > another file that keeps it from being traced, but can be enabled when > > you want it to. > > Yeah that would be cool. > > Personally I'm just using shell scripts that poke the files in sysfs, > and I'm often running on different boxes, so the more that just works > without extra config by me the better. Agreed, which is why I hope to get something like this in. Perhaps I'll aim for 3.12. Then we can look at all the functions with "notrace" and see which can be converted. Thanks, -- Steve _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
