Re: [PATCH] Fix for OProfile callgraph for Power 64 bit user apps

[Paul Mackerras]

Carl Love writes:

> The following patch fixes the 64 bit user code backtrace 
> which currently may hang the system.  

What exactly is wrong with it?

Having now taken a much closer look, I now don't think Nate Case's
patch addresses this, since it only affects constant size arguments
<= 8 to copy_{to,from}_user_inatomic.

However, I don't see why your patch fixes anything.  It means we do
two access_ok calls and two __copy_from_user_inatomic calls, for 8
bytes, at sp and at sp + 16, rather than doing one access_ok and
__copy_from_user_inatomic for 24 bytes at sp.  Why does that make any
difference (apart from being slower)?

Paul.
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