On 06.06.21 21:24, steve freyder via Xenomai wrote: > Hello Xenomai group, > > We're in the process of moving from Xenomai 3.0.7/4.1.18 to > 3.1/4.14.85. Testing one of our apps we found that select() was > returning -1 with errno == EADV. This app was written before we knew > about the recommendation from Philippe contained in this message: > > > https://xenomai.org/pipermail/xenomai/2019-August/041435.html > > > > We're not mixing Linux/Xenomai descriptors in the select set, the fd's > (4 of them in this case) are all pointing to Linux FIFOs > (/dev/somename{1..4}), and we'll ultimately start using __STD(select) > like the above msg says we should (until this was found we were unaware > of the importance of using __STD(select)). > > But my reason for posting is my confusion about the EADV return. The > message says: > >>>> Switch from -EBADF to -EADV to notify userland that RTDM does not >>>> manage a file descriptor, which cannot conflict with any sensible >>>> error code the Cobalt core or any RTDM driver may return. > > But also says: > >> We still want to receive -EBADF on wrong fildes appearing in select() >> descriptors. > > Taking both of those into account, I looked at the code in > lib/cobalt/select.c which implements the glibc fallback: > > if (err == -EBADF || err == -EPERM || err == -ENOSYS) > return __STD(select(__nfds, __readfds, > __writefds, __exceptfds, __timeout)); > > In the specific case of our app, had the above code included a check for > -EADV, things would operate as they did under 3.0.7. However, the > statement "still want to receive -EBADF on wrong fildes appearing in > select" suggests that the check for -EADV shouldn't be necessary. There > must be something at a lower level that is returning -EADV instead of > -EBADF when faced with a Linux FIFO fd, or, if -EADV is appropriate then > it seems adding a check for -EADV along with -EBADF, -EPERM, and -ENOSYS > is also appropriate if backwards compatibility is desired for select(). >
I had a regression report on this topic internally as well, but no proper reproduction case. Do you have a self-contained test for us? The goal is clear: EADV should remain internal, not visible by select() callers (or any other service, see 5f14ea8ae6d6). Jan -- Siemens AG, T RDA IOT Corporate Competence Center Embedded Linux
