possible deadline situation when reading NUL bytes

[knz]

See cockroachdb/cockroach#9607 for details.

[chzyer]

@knz Could you help me to test that can this pr fix this deadlock? Thanks.

[knz]

To test this properly I think there is no choice and you have to perform a stress test (many hundreds calls of the problem).
I tested with this:

for ((i=0;i<10000;i++)); do printf 'bye\x00' | ./readline-demo; done

No error found any more after 10000 runs, so the situation is now definitely better! 👍

[chzyer]

Thanks, @knz