The tests currently have a single writer thread updating the system
DSCR with a 1/1000 chance looped only 100 times. So only around one in
10 runs actually do anything.
* Add multiple threads to the dscr_explicit_random_test case.
* Use a barrier to make all the threads start work as simultaneously as
possible.
* Use a rwlock and make all threads have a reasonable chance to write to
the DSCR on each iteration.
PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP is used to prevent
writers from starving while all the other threads keep reading.
Logging the reads/writes shows a decent mix across the whole test.
* Allow all threads a chance to write.
* Make the chance of writing more likely.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230406043320.125138-6-bgray@linux.ibm.com
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