Ahh, good point. Similar situation occured on ARM when it went
preemptive. Thankfully, Russel King and company try to properly lock
things even if they are no ops.
Coding under a preemptive kernel means more than what
Documentation/preempt-locking.txt implies ... you have to protect data
regions as if you are operating under SMP.
It is good practice, anyhow.
This means you can include linux/spinlock.h and use the locking
constructs as needed. Under a normal UP kernel, they will compile
away. Under a preemptive kernel, they will provide the needed
reentrancy protection. If there ever is a an SMP SH kernel (or
something like it) the kernel will be ready for the future.
Robert Love
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