From: "Robert Netzlof" <[email protected]>
Sent: Monday, July 31, 2017 11:07 AM
On 7/30/17, Phil Smith <[email protected]> wrote:
Charles Mills wrote, in part:
The effect of multiple CPUs on a multi-task program is even worse than the
load, add, store example above. With two CPUs, it is possible for even
single machine instructions to interleave. So if one task executes MVC
FOO,=C'Now is the time for all good men to come to the aid of the party'
and
another CPU executes MVC FOO,=C'The quick brown fox jumps over the lazy
dog'
it is at least in theory* possible for FOO to end up containing 'Now is
the
time fox jumps over the lazy dog the aid of the party'.
Mmm...I'm pretty sure a single instruction is still atomic. I'm sure Peter
Relson or one of the other IBMers will chime in, but it there has to be some
sort of interlock at some level. And I've debugged plenty of concurrency
problems, never seen a mixture from a single instruction!
...phsiii
Not sure, but is not MVCL interruptible?
MVCL, CLCL etc are interruptible.
They have to be.
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