no support for fcntl?

[sxu55]

I found the following code will yield panic output in windows bash:

int flags = fcntl(fd, F_GETFL);
if (flags == -1)
panic("Could not set up async IO");

if (set)
flags |= FASYNC;
else
flags &= ~(FASYNC);

if (set) {
if (fcntl(fd, F_SETOWN, getpid()) == -1)
panic("Could not set up async IO");
}

if (fcntl(fd, F_SETFL, flags) == -1)
panic("Could not set up async IO");

[jackchammons]

We do not yet support O_ASYNC and the associated SIGIO signal that would be required for this to work as expected. We have opened a bug for this internally. Thanks for bringing this to our attention.

[stehufntdev]

@sxu55 can you please let us know what scenario you were trying or if this was a test? Also, do you know what type of file was being used (e.g. socket, pipe, ...)? Signal driven IO can only be enabled on a handful of types and we wanted to make sure we prioritize the ones of interest.

[sxu55]

@stehufntdev I encountered this situation when I tried to run an computer architecture simulator called gem5 in bash. The code that results in this issue is here: http://www.gem5.org/docs/html/pollevent_8cc_source.html
please let me know if you need more information

BTW, I am wondering if the bash in insider preview has much more bugs fixed than the current stable 14393 bash? Several days ago I encountered another issue with scala and sbt not able to run on oracle java 1.8 but can somewhat run on jdk7, but I've not tested it in insider preview version.

[benhillis]

@sxu55 - The Insider builds have a ton more functionality than the 14393 build. To get an idea of how much has been changed take a look at the release notes.

[sxu55]

perfect. thx

[stehufntdev]

Thanks for the reply. I looked through the code but it wasn't immediately obvious what type of what type of file was being used. Do you happen to know? If could you please take a strace of the scenario so we can check?

[sxu55]

I don't know.. Since I am currently not working on gem5 anymore, I will find some time later and run strace to collect what you need.

[stehufntdev]

Sounds great, thanks for the help!

[TheJare]

For the record, I just ran into this while using the Termbox-go library for text-mode UI apps (its written in Go, but the code is trivially similar to equivalent C code): https://github.com/nsf/termbox-go/blob/master/api.go#L30, basically:

in = open("/dev/tty", O_RDONLY, 0)
signal(SIGIO, handler)
fcntl(in, F_SETFL, O_ASYNC | O_NONBLOCK)
// And fails here with invalid argument, F_GETOWN also fails:
fcntl(in, F_SETOWN, getpid())

I have public WSL with Ubuntu 14.04, not the insider preview.

[stehufntdev]

Thanks for the follow-up. WSL does not current support signal driven IO on tty devices, but we are tracking the work. Please give us feedback on user voice for this scenario so we can prioritize - https://wpdev.uservoice.com/forums/266908-command-prompt-console-bash-on-ubuntu-on-windo/.

[therealkenc]

Brian marked this fixedinsiderbuilds last fall. Closing. If there are still failures in the OP test case (I didn't check), please re-file and we can do a reboot on the issue.