Re: emacs-nox hogs CPU if backgrounded during compile

[Ryan Johnson <ryan dot johnson at cs dot utoronto dot ca>]

On 27/08/2013 8:06 AM, Ken Brown wrote:
> 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?
I've attached a snippet of strace output; it is replicated endlessly in 
the log file I took, with increasing timestamps being the only 
difference AFAICT. The snippet itself in turn consists of a segment that 
is repeated three times, where the only meaningful difference is the 
value of "set_bits: me"

> And when you say this has always worked in the past, are you talking 
> about earlier versions of emacs or earlier versions of cygwin?
I migrated to 64-bit cygwin and emacs-24 at the same time (from 32-bit 
emacs-23), when my old computer's HDD died, so I don't have an easy way 
to answer that question. I didn't notice the problem at first, either, 
so I don't know if a subsequent update changed things (I doubt it, 
though, because I do remember a few times where emacs was hogging CPU 
and I didn't quite know what had happened, before I figured out what was 
going on).

HTH,
Ryan

Attachment: emacs-strace.txt
Description: Text document

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