| 119,21 → 119,20 |
|---|
| preemption and thread migration during times when preemption is |
| possible.</para> |
| |
| <para> |
| <mediaobject id="thread_states" xreflabel=""> |
| <figure> |
| <title>Transitions among thread states.</title> |
| |
| <mediaobject id="thread_states" xreflabel=""> |
| <imageobject role="html"> |
| <imagedata fileref="images/thread_states.png" format="PNG" /> |
| </imageobject> |
| |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/thread_states.svg" format="SVG" /> |
| </imageobject> |
| |
| <caption>Transitions among thread states.</caption> |
| </mediaobject> |
| </para> |
| |
| <imagedata fileref="images/thread_states.png" format="PNG" /> |
| </imageobject> |
| |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/thread_states.svg" format="SVG" /> |
| </imageobject> |
| </mediaobject> |
| </figure> |
| |
| <para>HelenOS userspace layer knows even smaller units of execution. Each |
| userspace thread can make use of an arbitrary number of pseudo threads. |
| These pseudo threads have their own synchronous register context, |
| 190,7 → 189,7 |
|---|
| essential. If the processor kept running using the stack of the |
| preempted thread it could damage it because the old thread can be |
| migrated to another processor and scheduled there. In the worst case |
| scenario, two execution flows would be using the same stack. </para> |
| scenario, two execution flows would be using the same stack.</para> |
| |
| <para>The scheduling policy is implemented in function |
| <code>find_best_thread</code>. This function walks the processor run |