Locking while executing bottom-halves and process context code

[Pratyush Patel]

Hello,

While reading a section in Linux Kernel Development, I came across the
following:

"If process context code and a bottom half share data, you need to
disable bottom-half processing and obtain a lock before accessing the
data."

Why is this the case? Can one not disable/lock the process context
code instead of the bottom-half and access data?

Similarly, for the statement,

"If interrupt context code and a bottom half share data, you need to
disable interrupts and obtain a lock before accessing the data."

Any help in clarifying this would be much appreciated.

Thanks,
Pratyush