The initial state is to have a prod_head and prod_tail pointing at the same location.
-Multiple Consumer Enqueue First Step
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Multiple Producers Enqueue First Step
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On both cores, *ring->prod_head* and ring->cons_tail are copied in local variables.
The prod_next local variable points to the next element of the table,
.. figure:: img/ring-mp-enqueue1.*
- Multiple consumer enqueue first step
+ Multiple producer enqueue first step
-Multiple Consumer Enqueue Second Step
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Multiple Producers Enqueue Second Step
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The second step is to modify ring->prod_head in the ring structure to point to the same location as prod_next.
This operation is done using a Compare And Swap (CAS) instruction, which does the following operations atomically:
.. figure:: img/ring-mp-enqueue2.*
- Multiple consumer enqueue second step
+ Multiple producer enqueue second step
-Multiple Consumer Enqueue Third Step
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Multiple Producers Enqueue Third Step
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The CAS operation is retried on core 2 with success.
.. figure:: img/ring-mp-enqueue3.*
- Multiple consumer enqueue third step
+ Multiple producer enqueue third step
-Multiple Consumer Enqueue Fourth Step
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Multiple Producers Enqueue Fourth Step
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Each core now wants to update ring->prod_tail.
A core can only update it if ring->prod_tail is equal to the prod_head local variable.
.. figure:: img/ring-mp-enqueue4.*
- Multiple consumer enqueue fourth step
+ Multiple producer enqueue fourth step
-Multiple Consumer Enqueue Last Step
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Multiple Producers Enqueue Last Step
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Once ring->prod_tail is updated by core 1, core 2 is allowed to update it too.
The operation is also finished on core 2.
.. figure:: img/ring-mp-enqueue5.*
- Multiple consumer enqueue last step
+ Multiple producer enqueue last step
Modulo 32-bit Indexes