RE: Spurious/undocumented EINTR from io_uring_enter

[Joseph Christopher Sible <jcsible@cert.org>]

On 4/7/20 5:42 PM, Jens Axboe wrote:
> Lots of system calls return -EINTR if interrupted by a signal, don't
> think there's anything worth fixing there. For the wait part, the
> application may want to handle the signal before we can wait again.
> We can't go to sleep with a pending signal.

This seems to be an unambiguous bug, at least according to the BUGS
section of the ptrace man page. The behavior of epoll_wait is explicitly
called out as being buggy/wrong, and we're emulating its behavior. As
for the application wanting to handle the signal, in those cases, it
would choose to install a signal handler, in which case I absolutely
agree that returning -EINTR is the right thing to do. I'm only talking
about the case where the application didn't choose to install a signal
handler (and the signal would have been completely invisible to the
process had it not been being traced).

Joseph C. Sible