bug#33194: 26.1; Auto-revert mode causes emacs to use 100% cpu whenever a file is being written to in the home directory

[Justin Van Winkle <justin.vanwinkle@gmail.com>]

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I checked out and installed from master (at
294a5246b264441d436612d4de0dd89fad130aa3).

I still see 100% cpu usage in emacs.

What I did:

In one terminal I run 'emacs' from my home directory, and I don't open any
files.
In another terminal, again while in the home directory, I run 'cat
/dev/zero > zed'.

Emacs cpu usage spikes to 100%.

- Justin

On Sun, Nov 4, 2018 at 6:58 AM Michael Albinus <michael.albinus@gmx.de>
wrote:

> Michael Albinus <michael.albinus@gmx.de> writes:
>
> Hi Justin,
>
> >> I mean it is certainly a bug to use 100% of a cpu just because a file
> >> that is in the same directory to a file you are editing is being
> >> written to, but it may not be unintentional behavior.
> >
> > I could reproduce the problem. I have a running Emacs for some days, and
> > I've enabled `global-auto-revert-mode'. Starting scp copy of a large
> > file outside Emacs, brought Emacs up to 100% cpu usage.
>
> I have pushed a fix for this to Emacs' master branch in git. The case of
> several buffers using the same file notification descriptor was prepared
> already in the code; due to a silly bug it didn't work.
>
> > The variable `file-notify-descriptors' contains ...
> >
> > As we can see, many identical entries #s(file-notify--watch
> > /home/albinus nil auto-revert-notify-handler).
> > Every incoming event for "/home/albinus" triggers the many calls of
> > `auto-revert-notify-handler', although one entry would be sufficient. I
> > will check, where all these entries come from.
>
> This doesn't happen any longer for me. And Emacs doesn't eat all cpu
> time.
>
> Do you have a chance to build Emacs 27.0.50, for verification?
>
> Best regards, Michael.
>

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