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+[[!meta copyright="Copyright © 2010, 2012, 2013 Free Software Foundation,
+Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+[[!tag open_issue_gnumach]]
+
+[[Mach]] internally uses *[[/continuation]]*s for kernel [[thread]] management.
+
+The advantage is that not a full kernel thread stack has to be preserved in
+case that a thread is about to enter a blocking state.  This saves space.  It
+is not clear this is still worthwhile given today's RAM offerings.  (How many
+kernel threads are there, typically?)
+
+And, this would no longer be possible in case Mach were be made a
+[[preemptive|preemption]] kernel.  In the latter case, the kernel itself, that
+is, kernel threads can be preempted, and then their full state needs to be
+preserved.
+
+See also [[open_issues/multithreading]].