emacs-nox hogs CPU if backgrounded during compile

[Ken Brown]

On 8/27/2013 4:28 AM, Ryan Johnson wrote:
> On 17/08/2013 2:41 PM, Ryan Johnson wrote:
>> Hi all,
>>
>> The following STC causes emacs-nox to peg a CPU indefinitely. Emacs
>> remains responsive, but C-c C-k doesn't kill the compile; you have to
>> exit emacs to remove the "Compiling" status. Killing the buffer or
>> starting a new compile offers to kill the offending process, but doesn't.
>>
>> Attaching gdb shows an endless loop inside
>> kernelbase.dll!RaiseException, but provides no other clues that I
>> could see.
>>
>> 1. emacs-nox -Q
>> 2. M-x compile
>> 3. C-a C-k sleep 1; echo hi
>> 4. ^Z (before the sleep finishes)
>> 5. fg (after the sleep finishes)
>>
>> I don't know if this is related to limited pipe buffering, but I don't
>> think so: it has always worked in the past, and the the 3-4 bytes
>> required to buffer up "hi\n" is hardly onerous.
>>
>> $ uname -a
>> CYGWIN_NT-6.1 ryan-laptop-v02 1.7.24(0.269/5/3) 2013-08-15 11:59
>> x86_64 Cygwin
>>
>> $ cygcheck -cd
>> bash                      4.1.11-1
>> cygwin                    1.7.24-1
>> emacs                     24.3-5
>> mintty                    1.2-beta1-1
 > Ping... is anyone else at least able to reproduce this?

I can reproduce this on both x86 and x86_64, even without the "echo hi". 
  Since gdb doesn't seem to be helping, have you tried strace?  And when 
you say this has always worked in the past, are you talking about 
earlier versions of emacs or earlier versions of cygwin?  In either 
case, you could try a bisection to see when the problem first appeared.

I don't have time to try this myself right now.

Ken

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