bug#34260: 27.0.50; Emacs randomly hangs during redisplay

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[John Shahid]

I have updated to the latest master a while ago and since then my Emacs
have been acting weird and becomes unusable.  I tried to turn on
debug-on-quit but I Emacs is always inside redisplay when I hit C-g.
Almost always the stacktrace has somewhere a call to `message` which in
turn calls `redisplay` and it just hangs and consumes 100% of the cpu.
I tried to debug the proces using gdb and found out that Emacs is always
inside `redisplay_internal' when I stop it using `kill -TSTP emacs'.

Worth noting that this problem isn't predictable and is hard to
reproduce.  It also might be related to EXWM and commit `e567ac1495'.

> 436c225f1b * Unbreak the macOS NS build
> 957090b795 *   Merge from origin/emacs-26
>            |\
> c9f6f86814 | * Prevent redrawing if frame is garbaged
> 00ba2267ed | * Attempt to fix hangs on MS-Windows due to C-g
> e567ac1495 * | Run window change functions during redisplay

I reverted my local copy of Emacs to '470082de55: List lengths are
always fixnums now' and haven't ran into any issues since then.

Let me know how I can debug this issue further.  Would the display
engine trace help in this case ?  Emacs doesn't enter an infinite
recursion but from the CPU usage it is entering some sort of infinite
loop, but I can't figure out why.


In GNU Emacs 27.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version 3.24.4)
 of 2019-01-30 built on amun
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bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[Michael Heerdegen]

John Shahid <jvshahid@gmail.com> writes:

> Let me know how I can debug this issue further.  Would the display
> engine trace help in this case ?  Emacs doesn't enter an infinite
> recursion but from the CPU usage it is entering some sort of infinite
> loop, but I can't figure out why.

What you write reminds me of the bug I (a user) had reported: Bug
#34179.  Maybe you can check whether you are experiencing the same
issue?  There are suggested patches in this thread that fixed the hangs
for me.


Michael.

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Date: Wed, 30 Jan 2019 22:46:26 +0100
> Cc: 34260@debbugs.gnu.org
> 
> John Shahid <jvshahid@gmail.com> writes:
> 
> > Let me know how I can debug this issue further.  Would the display
> > engine trace help in this case ?  Emacs doesn't enter an infinite
> > recursion but from the CPU usage it is entering some sort of infinite
> > loop, but I can't figure out why.
> 
> What you write reminds me of the bug I (a user) had reported: Bug
> #34179.

Certainly sounds like the same bug.

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[martin rudalics]

 > Let me know how I can debug this issue further.  Would the display
 > engine trace help in this case ?  Emacs doesn't enter an infinite
 > recursion but from the CPU usage it is entering some sort of infinite
 > loop, but I can't figure out why.

Please tell me if the following hold when the hang occurs:

(1) You have at least two frames open.

(2) You run an externl process (likely shell) in a non-selected frame.

(3) The minibuffer window of the selected frame is or should be enlarged.

Thank you, martin

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[John Shahid]

martin rudalics <rudalics@gmx.at> writes:

>> Let me know how I can debug this issue further.  Would the display
>> engine trace help in this case ?  Emacs doesn't enter an infinite
>> recursion but from the CPU usage it is entering some sort of infinite
>> loop, but I can't figure out why.
>
> Please tell me if the following hold when the hang occurs:
>
> (1) You have at least two frames open.

Yes.  EXWM creates a frame per monitor.  I have two monitors which is
equivalent to two frames.  I verified that by running `(frame-list)'
which gave me the following `(#<frame *Minibuf-1* 0x915df20> #<frame
*eshell* 0x1408c30>)'.

> (2) You run an externl process (likely shell) in a non-selected frame.

Very likely.  I didn't what to look for when this happened, but I almost
always have an eshell/ansi-term window open.

> (3) The minibuffer window of the selected frame is or should be enlarged.

I am not sure.  In the stacktraces I looked at there was always a call
to `message', but I'm not sure what are the args to it.  Due to the
nature of my setup (i.e. using EXWM/Emacs as the window manager), when
this happen it is little hard to debug from inside Emacs and I have to
use gdb.  I am not sure how to get the args from gdb.

JS

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[martin rudalics]

 >> (3) The minibuffer window of the selected frame is or should be enlarged.
 >
 > I am not sure.  In the stacktraces I looked at there was always a call
 > to `message', but I'm not sure what are the args to it.  Due to the
 > nature of my setup (i.e. using EXWM/Emacs as the window manager), when
 > this happen it is little hard to debug from inside Emacs and I have to
 > use gdb.  I am not sure how to get the args from gdb.

Never mind.  I'm afraid that EXWM is much too refined in its use of
frame/window features as to make its parsing possible for anyone but
its author.

I hope to post a fix for Bug#34179 by the end of this week.  If it
doesn't work for you then we'll have to contact Chris Feng.

martin

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[John Shahid]

martin rudalics <rudalics@gmx.at> writes:

>>> (3) The minibuffer window of the selected frame is or should be enlarged.
>>
>> I am not sure.  In the stacktraces I looked at there was always a call
>> to `message', but I'm not sure what are the args to it.  Due to the
>> nature of my setup (i.e. using EXWM/Emacs as the window manager), when
>> this happen it is little hard to debug from inside Emacs and I have to
>> use gdb.  I am not sure how to get the args from gdb.
>
> Never mind.  I'm afraid that EXWM is much too refined in its use of
> frame/window features as to make its parsing possible for anyone but
> its author.
>
> I hope to post a fix for Bug#34179 by the end of this week.  If it
> doesn't work for you then we'll have to contact Chris Feng.

Sounds good.  Thanks Martin.  A side question, is there a way to get
notification on a specific bug in debbugs ?

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[martin rudalics]

 >> I hope to post a fix for Bug#34179 by the end of this week.  If it
 >> doesn't work for you then we'll have to contact Chris Feng.
 >
 > Sounds good.  Thanks Martin.

Please try now with latest master and report any anomalies you still
observe.

 > A side question, is there a way to get
 > notification on a specific bug in debbugs ?

Notification in which sense?  The bug tracker should have confirmed
that you posted the bug and should inform you as soon as it is closed.
You will get any messages sent to the bug number if you are either
subscribed to bug-gnu-emacs or you're CC-ed in the message (the latter
being something most subscribers of bug-gnu-emacs do).

Thanks, martin

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[John Shahid]

martin rudalics <rudalics@gmx.at> writes:

>>> I hope to post a fix for Bug#34179 by the end of this week.  If it
>>> doesn't work for you then we'll have to contact Chris Feng.
>>
>> Sounds good.  Thanks Martin.
>
> Please try now with latest master and report any anomalies you still
> observe.

Thank you.  I compiled master and running it locally.  I will let you
know as soon as I notice anything weird.

JS

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[John Shahid]

I haven't noticed any hangs locally.  I think this bug can be closed.
Thanks Martin!

Cheers,

JS

John Shahid <jvshahid@gmail.com> writes:

> martin rudalics <rudalics@gmx.at> writes:
>
>>>> I hope to post a fix for Bug#34179 by the end of this week.  If it
>>>> doesn't work for you then we'll have to contact Chris Feng.
>>>
>>> Sounds good.  Thanks Martin.
>>
>> Please try now with latest master and report any anomalies you still
>> observe.
>
> Thank you.  I compiled master and running it locally.  I will let you
> know as soon as I notice anything weird.
>
> JS

bug#34260: 27.0.50; Emacs randomly hangs during redisplay

[martin rudalics]

fixed 34260 27.1
quit

 > I haven't noticed any hangs locally.  I think this bug can be closed.

Done.

Thank you, martin