On 6/6/24 10:22 AM, Jeff King wrote: > Since 18d8c26930 (test_terminal: redirect child process' stdin to a pty, > 2015-08-04), we set up a pty and copy stdin to the child program. But > this ends up being racy; once we send all of the bytes and close the > descriptor, the child program will no longer see a terminal! isatty() > will return 0, and trying to read may return EIO, even if we didn't yet > get all of the bytes. > > This was mentioned even in the commit message of 18d8c26930, but we > hacked around it by just sending an infinite input from /dev/zero (in > the intended case, we only cared about isatty(0), not reading actual > input). > > And it came up again recently in: > > https://lore.kernel.org/git/d42a55b1-1ba9-4cfb-9c3d-98ea4d86da33@xxxxxxxxx/ > > where we tried to actually send bytes, but they don't always all come > through. So this interface is somewhat of an accident waiting to happen; > a caller might not even care about stdin being a tty, but will get bit > by the flaky behavior. > > One solution would probably be to avoid closing test_terminal's end of > the pty altogether. But then the other side would never see EOF on its > stdin. That may be OK for some cases, but it's another gotcha that > might cause races or deadlocks, depending on what the child expects to > read. > > Let's instead just drop test_terminal's stdin feature completely. Since > the previous commit dropped the two cases from t4153 for which the > feature was originally added, there are no callers left that need it. > > Signed-off-by: Jeff King <peff@xxxxxxxx> Acked-by: Rubén Justo <rjusto@xxxxxxxxx>
