the creation of boot_cpu_init() is wrong and accessinguninitialised data

[James Bottomley]

The basic problem with this function is that on most architectures
smp_processor_id() is an alias for current_thread_info()->cpu which
isn't given its correct value until setup_arch(), so adding a
boot_cpu_init() that uses it *before* setup_arch() is called is plain
wrong.  You manage to get away with it 99% of the time because its
uninitialised value is zero and mostly the id of the booting CPU is
zero ... but guess who's got a box currently booting on CPU 1 with no
CPU 0?

Unfortunately, I can't think of a good solution for what you want to do.
The thing that looks most plausible is hard_smp_processor_id() which
reads the actual register value of the processor id.  However, on x86
(and any other architectures that renumber their CPUs in setup_arch())
this will ultimately turn out wrong again.

James


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