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
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lwsync Memory Barrier for Release Operation<br />
The A and B sets consist of all memory access <strong>in</strong>structions preced<strong>in</strong>g<br />
and follow<strong>in</strong>g <strong>the</strong> lwsync, respectively.<br />
Only <strong>the</strong> follow<strong>in</strong>g pairs of ai, bj <strong>in</strong>structions are ordered:<br />
A-side load → B-side load<br />
A-side load → B-side store<br />
A-side store → B-side store<br />
Thus, A-side store → B-side load are not ordered.<br />
The dcbz data cache block zero is counted as a store.<br />
It’s used e.g. to implement a release:<br />
stwx r1,r2,r3 # modify shared data...<br />
stwx r4,r5,r6<br />
...<br />
stwx r29,r30,r31 # last write <strong>in</strong> critical section<br />
lwsync<br />
stwx r8,r9,r10 # set lock to free<br />
Jonas Skeppstedt (js@cs.lth.se) Lecture 6 2013 51 / 70