Martin Lucina wrote:
Ulrich.Windl@rz.uni-regensburg.de said:
Hi!
I think a problem with your test program is that you don't wait for the write() thread to finish before you try to read the mmap(). See how locking on a producer-consumer (or reader-writer) relationship is usually implemented (If you don't have it ready, I could send you the algorithms).
That shoudln't matter.
More to the point, you don't wait for the write() thread to *start* - there's
no guarantee that it will actually start running as soon as the barrier is
released. A valid test has to know that the write() thread actually got
scheduled and ran.
The write thread opens the file descriptor with
O_DSYNC, and all the test program is trying to verify is that the mmap
eventually becomes consistent. You can ignore the pthread_barrier stuff,
that just tries to eliminate thread creation time from the equation.