At 14:28 -0500 on 12/20/2010, Gerhard Postpischil wrote about Re:
X-memory POST question:
On 12/20/2010 11:28 AM, Charles Mills wrote:
A task in address space A issues a WAIT on an ECB in CSA (SP 241).
A task in address space B wishes to POST that ECB. Must it use an X-memory
POST (ASCB=A)?
I see that you've already gotten a solution, but the strict answer
is no. If the ECB is not being waited on, you can post it with a
Compare-and-Swap and save some overhead.
I assume that this is safe since you can not stop being the running
task between the test and your updating the ECB (and there is not
another running thread/task on another engine/cpu which could be
dispatching Address Space A). The use of CS is not an issue given the
fact that the query STATED that Address Space A has already done the
WAIT unless you are considering the case where Address Space B does
the POST or CS before Address Space A does the WAIT (so the WAIT code
finds the ECB already posted or the AS A code does a pre-WAIT test of
the ECB to bypass the need to WAIT).
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