From: Ken Brown <kbrown@cornell.edu>
To: "cygwin@cygwin.com" <cygwin@cygwin.com>
Cc: Jon TURNEY <jon.turney@dronecode.org.uk>
Subject: Re: Regression (last snapshot)
Date: Wed, 31 Jul 2019 15:53:00 -0000 [thread overview]
Message-ID: <8e57d4da-722d-1b9a-bd28-5f96ed182f6a@cornell.edu> (raw)
In-Reply-To: <c5d01965-80b9-cece-54d2-f7462f84c0a2@cornell.edu>
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 3668 bytes --]
On 7/29/2019 2:55 PM, Ken Brown wrote:
> On 7/29/2019 11:40 AM, Corinna Vinschen wrote:
>> On Jul 29 17:23, Corinna Vinschen wrote:
>>> On Jul 29 14:26, Ken Brown wrote:
>>>> On 7/29/2019 9:47 AM, Corinna Vinschen wrote:
>>>>> On Jul 29 13:18, Ken Brown wrote:
>>>>>> $ strace -o trace.out ls -lL <(grep bash .bashrc)
>>>>>> ls: cannot access '/dev/fd/63': No such file or directory
>>>>>
>>>>> No, please run bash:
>>>>>
>>>>> strace -o trace.out bash -c 'ls -lL <(grep bash .bashrc)'
>>>>>
>>>>> Otherwise there's no process actually creating the pipe, given the <()
>>>>> expression is a bash expression.
>>>>
>>>> Yes, of course. I should have realized this since it's exactly what I
>>>> did under gdb. Anyway, the result is the same as it was under gdb: If
>>>> I run the command under strace, I don't see the broken pipe error.
>>>>
>>>> Is it possible that debugging causes an fd to the read end of the pipe
>>>> to stay open longer, thereby preventing the error?
>>>
>>> The fact that you observe it sporadically points to a race condition.
>>> Debugging serializes stuff usually running in parallel, potentially
>>> eliminating the race.
>>
>> Is there any chance this is a BLODA problem?
>
> I doubt it. I'm seeing this on two different computers, and I haven't seen any
> other symptoms suggesting BLODA.
>
>> If /dev/fd/63 doesn't
>> exist in ls, it would mean ls didn't inherit the FIFO, which sounds
>> very unlikely.
>
> Actually I never saw an ls error saying /dev/fd/63 doesn't exist, except in my
> incorrect run of strace.
>
> Here's the error that I can reproduce easily in xterm:
>
> $ ls <(grep bash .bashrc)
> /dev/fd/63
> grep: write error: Broken pipe
>
> This happens 98% of the time. Notice that I used plain 'ls' rather than the
> original 'ls -lL'. With the latter, I get the broken pipe error 60% of the time
> rather than 98%:
>
> $ ls -lL <(grep bash .bashrc)
> pr-------- 1 kbrown None 0 2019-07-29 14:46 /dev/fd/63
> grep: write error: Broken pipe
>
> What about the explanation I tried earlier, but perhaps not clearly: ls prints
> /dev/fd/63 and then exits, thereby closing the read end of the pipe, while grep
> (running asynchronously) hasn't finished writing to the write end of the pipe.
>
> The fact that I get the broken pipe error more often with plain 'ls' than with
> 'ls -lL' is consistent with that. And the fact that I get no errors with 'cat
> <(grep bash .bashrc)' is also consistent with it, since cat doesn't exit until
> grep has finished writing.
>
> On the other hand, this doesn't explain why I see the error only under xterm,
> nor does it explain why you can't reproduce it at all.
I've made some progress. It turns out that the problem only occurs in terminals
launched from the xwin-xdg-menu tray icon. I can even launch a mintty window
from that icon (System Tools -> Cygwin Terminal) and I'll see the problem. On
the other hand, I can launch an xterm without using that icon (e.g., 'DISPLAY=:0
xterm -l&' from a mintty window) and I won't see the problem.
So the issue has something to do with how xwin-xdg-menu launches applications,
and how that interacts with bash's process substitution. I've just downloaded
the xwin-xdg-menu source and will see if I can figure out what's going on. I've
also added Jon to the CC in case he has a chance to take a look.
Ken
\x03BKCB\x1cØ\x19[H\x1c\^[Ü\x1cÎ\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0eËØÞYÝÚ[ÛÛKÜ\x1cØ\x19[\Ë\x1d^[[\x03BTN\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0eËØÞYÝÚ[ÛÛKÙ\KÃB^[ØÝ[Y[\x18]\x1a[Û\b\b\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0eËØÞYÝÚ[ÛÛKÙ^[ØÜË\x1d^[[\x03B[ÝXØÜXH\x1a[Î\b\b\b\b\b\x1a\x1d\x1d\x1c\x0eËØÞYÝÚ[ÛÛKÛ[\vÈÝ[ÝXØÜXK\Ú[\^[\x19CBB
next prev parent reply other threads:[~2019-07-31 15:53 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-20 22:55 Houder
2019-07-21 9:38 ` Houder
2019-07-21 9:42 ` Houder
2019-07-22 12:23 ` Ken Brown
2019-07-22 13:44 ` Ken Brown
2019-07-22 15:20 ` Corinna Vinschen
2019-07-22 15:53 ` Corinna Vinschen
2019-07-22 16:45 ` Corinna Vinschen
2019-07-22 18:47 ` Houder
2019-07-26 22:12 ` Ken Brown
2019-07-27 0:14 ` Ken Brown
2019-07-27 10:21 ` Houder
2019-07-27 15:24 ` Ken Brown
2019-07-27 16:25 ` Houder
2019-07-29 8:45 ` Corinna Vinschen
2019-07-29 13:18 ` Ken Brown
2019-07-29 13:35 ` Ken Brown
2019-07-29 13:48 ` Corinna Vinschen
2019-07-29 13:47 ` Corinna Vinschen
2019-07-29 14:26 ` Ken Brown
2019-07-29 15:23 ` Corinna Vinschen
2019-07-29 15:40 ` Corinna Vinschen
2019-07-29 18:56 ` Ken Brown
2019-07-31 15:53 ` Ken Brown [this message]
2019-07-31 18:00 ` Ken Brown
2019-08-01 9:01 ` Corinna Vinschen
2019-08-01 14:27 ` Jon Turney
2019-08-01 15:30 ` Ken Brown
2019-08-01 15:38 ` Eric Blake
2019-08-01 16:04 ` Corinna Vinschen
2019-08-01 21:17 ` Ken Brown
2019-08-02 2:32 ` Ken Brown
2019-08-02 14:34 ` Ken Brown
2019-08-02 15:04 ` Corinna Vinschen
2019-08-02 21:26 ` Brian Inglis
2019-08-02 21:53 ` Ken Brown
2019-08-02 21:58 ` Eric Blake
2019-08-03 3:50 ` Brian Inglis
2019-08-03 13:14 ` Ken Brown
2019-08-04 16:52 ` Houder
2019-08-01 10:03 ` Houder
2019-08-01 10:46 ` Houder
2019-08-01 12:20 ` Ken Brown
2019-08-01 14:29 ` Houder
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8e57d4da-722d-1b9a-bd28-5f96ed182f6a@cornell.edu \
--to=kbrown@cornell.edu \
--cc=cygwin@cygwin.com \
--cc=jon.turney@dronecode.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).