On 4/18/2020 5:48 PM, Ken Brown via Cygwin wrote:
On 4/18/2020 11:24 AM, sten.kristian.ivars...@gmail.com wrote:
Hey all
We're trying to nail down some issues with using named pipes
The issue we're getting is deterministic (ENXIO) but it is not this one, but
we think this issue is worth reporting anyway
We're using the branch topic/fifo
The program explained in short is:
- One main (parent) pipe that lives through the whole execution
- The main process forks 'children' child-processes that creates their own
(unique) named pipes
- Each child forks 'children' grans-child-processes that just writes some
bogus messages back to the unique child pipe
- Each child writes a bogus message back to the main process
- Every process creates a write and a read descriptor, but the write
descriptor is just a dummy descriptor (to somehow keep the pipe alive
without being bombarded with signals)
- This iterates a few times
Some of the constructs may be a bit confusing and maybe not relevant to this
issue, but I left them in the test-program anyway
Issue #1 sometimes occurs in line 35 (printed as 36) we get ENOENT (No such
file or directory) despite that the pipe was just created and the read
descriptor successfully was opened
*wfd = open(name, O_WRONLY);
Issue #2 sometimes occurs in line 73 (printed as 74) we get EBUSY (Device or
resource busy) when attempting to open a non blocking descriptor
const int wfd = open(name, O_WRONLY | O_NONBLOCK);
Issue #3 sometimes occurs somewhere unknown and the main process just get
stuck (I've failed to reproduced that with strace or so) and to not have any
more input so maybe this should be left out ?
I hope this is well described and hopefully it's enough to reproduce the
issue(s) and hopefully is not due to a fault test case ;-)
I'm just in the middle of fixing some bugs that are probably related. I hope to
have some fixes in the next day or two, as well as better error codes. (The
error codes are mostly translated from NTSTATUS codes and often don't reflect
the real problem.)
By the way, I really appreciate all your testing and bug reports. The FIFO code
is fairly new and hasn't gotten any intense testing up to now, especially in the
non-blocking case.
I've made some improvements in the opening of writers, which I will push soon
(probably tomorrow). I think that this will fix the errors you've been seeing
when opening writers. The issue is one of timing. I hope I've built in a large
enough timeout so that you won't see these errors anymore. But if it does fail
you should see ETIMEDOUT instead of EBUSY or ENOENT.
But there's a separate issue: Your program has two processes trying to read from
/tmp/pipe_parent at the same time. My implementation of support for multiple
readers is not yet finished, so this can't work yet. I hope to have at least a
first cut of this done within a few days.
Ken
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