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Does the exclusive access local address monitor hold the address of the access ?

Applies to: ARM11 processors


Refer to the ARM architecture reference manual v6 (issue I), section A2.9.1 for a description of
the exclusive access monitor.

The CPU should only tag one physical address at a time. If the CPU issues LDREX for address A,
this should be followed by an STREX for address A, before an LDREX for a different address B can
be issued.

Therefore, it is not necessary for the local address monitor to store the address of the
exclusive tag. The ARM states:


The IMPLEMENTATION DEFINED options for the local monitor are consistent with the local monitor
being constructed in a manner that it does not hold any physical address, but instead treats all
accesses as matching the address of the previous LDREX."

So the local monitor needs to hold only the exclusive access state (exclusive or open) and not
the address.

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