| Date | Fri, 25 Jan 2013 16:59:34 +0000 | From | Dave Martin <> | Subject | Re: [PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND |
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On Fri, Jan 25, 2013 at 11:44:14AM -0500, Steven Rostedt wrote: > [ I got an error with linux-arm-kernel@list.infradead.org and had to > remove from CC ]
Blame Arnd :)
> > On Fri, 2013-01-25 at 16:26 +0000, Dave Martin wrote: > > > However, if the purpose if making return_address() notrace is just to > > prevent infinite recursion, where finite recursion is safe, then it > > feels fixable as described above. > > > > Steven, do you know whether such an approach might be safe? > > > > I rewrote the function trace recursion code (see linux-next). The > function tracer wont recurse on itself. If the return_address() is only > used by callbacks and not directly by the mcount(ftrace_caller), then > after the first trace, ftrace wont let recursion of the callback. IOW, > callbacks of ftrace don't need to worry about re-entrancy at the same > context level (but do for different contexts, ie. normal, irq, softirq > and NMI). > > (commit edc15cafcbfa3d73f819cae99885a2e35e4cbce5 in linux-next and > friends)
Cool. Are you aware of return_address being used elsewhere? Currently I'm not aware of anything else which uses it, and grep is not finding any calls outside ftrace.h that I can see.
Cheers ---Dave
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