Chapter 1: Introduction and Overview
create_new_namespace
clone_nsproxy
copy_mnt_ns
put_uts_ns
put_mnt_ns
copy_utsname
Error?
Error?
Return error
NO
NO
YES
YES
YES
NO
new_ns->put_ns
not NULL?
new_ns->
mnt_ns not
NULL?
copy_utsname
return result
return-ENOMEM
kmem_cache_free
Error?
Error?
1
1
Figure 1-15: Example of a faithful, but unclear and convoluted code flow diagram.
Instead I employ code flow diagrams that illustrate the essential tasks performed by a function.
Figure 1-16 shows the code flow diagram that I would have employed instead of Figure 1-15.
copy_namespaces
clone_nsproxy
copy_mnt_ns
copy_utsname
copy_ipcs
Figure 1-16: Example of the style
of code flow diagrams used in
this book. They allow
immediately catching all
essential actions without being
distracted by nonessential
standard tasks.
The diagram omits several things, but this is on purpose, and also essential. By looking at the
figure, you will not see every detail of the function implementation, but you will instead imme-
diately realize that the kernel uses a specific routine to create a clone of each namespace, and
the function names provide a sufficient hint of which namespace is copied. This is much more
important!
