Threads in the new ISO C Standard from 2011
Threads in the new ISO C Standard from 2011
Threads in the new ISO C Standard from 2011
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Load and Reserve/Store Conditional Behaviour<br />
The load <strong>in</strong>struction fetches data <strong>from</strong> a memory location, and makes<br />
a reservation R <strong>in</strong> memory.<br />
If a different processor modifies <strong>the</strong> same memory location, <strong>the</strong><br />
reservation R is lost.<br />
If/when <strong>the</strong> processor with a reservation makes a conditional store,<br />
<strong>the</strong> memory location is modified only if <strong>the</strong> reservation was not lost <strong>in</strong><br />
between.<br />
Therefore it’s an atomic read-modify-write.<br />
The stwcx. conditional store <strong>in</strong> Power sets a condition code to<br />
<strong>in</strong>dicate whe<strong>the</strong>r <strong>the</strong> store succeeded or not (<strong>the</strong> dot <strong>in</strong> <strong>the</strong> mnemonic<br />
<strong>in</strong>dicates that <strong>the</strong> condition code is set by an operation on Power).<br />
Jonas Skeppstedt (js@cs.lth.se) Lecture 6 2013 48 / 70