Re: [PATCH 19/19] [INCOMPLETE] ARM: make return_address availablefor ARM_UNWIND

[Steven Rostedt]

[ I got an error with linux-arm-kernel@xxxxxxxxxxxxxxxxxx and had to
remove from CC ]

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)

-- Steve


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