On Thu, Oct 24, 2019 at 12:57 PM David Howells [off-list ref] wrote:

pipe: Add fsync() support

The keyrings testsuite needs the ability to wait for all the outstanding
notifications in the queue to have been processed so that it can then go
through them to find out whether the notifications it expected have been
emitted.

Can't you just do

    ioctl(fd, FIONREAD, &count);

in a loop instead? "No paperwork. Just sprinkle some msleep() crack on
him, and let's get out of here"

               Linus