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authorThomas Schwinge <thomas@schwinge.name>2010-12-15 22:29:07 +0100
committerThomas Schwinge <thomas@schwinge.name>2010-12-15 22:29:07 +0100
commite08610c5572f80bb148b2155cf18c8b8bc6c7e5f (patch)
treea54e9aff90e4bd248e4c9cc66fe12324a6bfc3f5
parent222852275554e45f4965dfa8fe6a7b5078649b01 (diff)
microkernel/mach/continuation: New.
-rw-r--r--microkernel/mach/continuation.mdwn24
-rw-r--r--open_issues/multithreading.mdwn3
2 files changed, 27 insertions, 0 deletions
diff --git a/microkernel/mach/continuation.mdwn b/microkernel/mach/continuation.mdwn
new file mode 100644
index 00000000..7a3267f3
--- /dev/null
+++ b/microkernel/mach/continuation.mdwn
@@ -0,0 +1,24 @@
+[[!meta copyright="Copyright © 2010 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]]."]]"""]]
+
+[[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|preemtion]] kernel. In the latter case, the kernel itself, that
+is, kernel threads can be preempted, and then their full state needs to be
+preserved.
+
+[[!tag open_issue_documentation]] <!-- Not linked to from any Mach page. Move
+to GNU Mach pages, as this is only an implementation detail? -->
diff --git a/open_issues/multithreading.mdwn b/open_issues/multithreading.mdwn
index 170734fd..39203333 100644
--- a/open_issues/multithreading.mdwn
+++ b/open_issues/multithreading.mdwn
@@ -22,6 +22,9 @@ Alternative approaches:
* Continuation-passing style
+ * [[microkernel/Mach]] internally [[uses
+ continuations|microkernel/mach/continuation]], too.
+
* [[Erlang-style_parallelism]]
* [libtcr - Threaded Coroutine Library](http://oss.linbit.com/libtcr/)