long I/O delays when strace is running

Daniel Santos daniel.santos@pobox.com
Fri Apr 21 07:57:00 GMT 2017

On 04/20/2017 08:43 AM, Gluszczak, Glenn wrote:
> I haven't run Cygwin Expect for about 6 moths on Windows but it was behaving fine last time I did.
> One thing I am aware of is you can't interrupt sleep in TCL.  The sleep must
> complete until the Control C is processed (regardless of whether you redirected signals
> to your own routines).  Otherwise signals seemed to be processed immediately.

Please note that my simplified test case isn't using expect, but the 
standard /usr/bin/sleep.exe -- this is just to have strace run and trace 
for a longer amount of time in order to expose the problem. (it did get 
broken into a new line though, so add a backslash:

> for ((i = 0; i < 64; ++i)); do strace --output=/tmp/sleep.$$.log \
> --trace-children --mask=startup sleep 64; done

> Perhaps some other service is interfering.  You may want to disable other services.
> Glenn

I usually disable most services, I can probably disable a few more, but 
I would like if somebody can run the above test case in one terminal 
windows and in the other terminal window do a simple ps -ef and let me 
know if ps responds immediately or has a delay.  I am using Windows 7, 
so it could be isolated to that windows version as well.  When I do 
this, ps has a 3 second delay while in 
fhandler_base_overlapped::wait_overlapped, but I've seen this delay in 
other processes while calling something like "open_shared."

Anyway, I'm going to try to find another simple test case that causes 
more of a drastic delay.


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