We don't actually need spinlocks here.
For user_copy(), we are checking that the pointer/size passed in
from user mode represents an area that the thread can read or
write to. Then we do a memcpy into the kernel-side buffer,
which is used from then on. It's OK if another thread scribbles
on the buffer contents during the copy, as we have not yet
begun any examination of its contents yet.
For the z_user_string*_copy() functions, it's also possible
that another thread could scribble on the string contents,
but we do no analysis of the string other than to establish
a length. We just need to ensure that when these functions
exit, the copied string is NULL terminated.
For SMP, the spinlocks are removed as they will not prevent a
thread running on another CPU from changing the buffer/string
contents, we just need to safely deal with that possibility.
For UP, the locks do prevent another thread from stepping
in, but it's better to just safely deal with it rather than
affect the interrupt latency of the system.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
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