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#63865
29.0.90; call-process while owning the X selection hangs other processes
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> From: Spencer Baugh <sbaugh <at> janestreet.com>
> Cc: luangruo <at> yahoo.com, 63865 <at> debbugs.gnu.org
> Date: Sat, 03 Jun 2023 10:12:41 -0400
>
> Eli Zaretskii <eliz <at> gnu.org> writes:
>
> > Really? "tons of places where it will run for prolonged periods of
> > time"? what is "prolonged period of time" for this purpose? Aren't
> > you a tad exaggerating?
>
> "prolonged period of time" is anything over a second.
>
> I see tons of calls to call-process with potentially long-running
> programs. "find", "gcc", "grep", "awk"... and depending on the user's
> system, *any* subprocess call can potentially run for a long time.
Please be specific. For example, "grep" runs in an async subprocess;
we run it with call-process when we probe it for support of some
command-line option. If you can show that these calls take "prolonged
period of time", please describe what you do and show the timing.
> But again, the point isn't just that they can potentially run for a long
> time. It's that *the user's whole system can be unusable* while they
> run. We are not just blocking Emacs, we are (sometimes) blocking
> *everything*.
AFAIU, the only "everything" that is blocked is an application that
happens to request an X selection at that precise time. That should
be rare for short enough call-process runs, since the same user is
doing that.
> (defun my-call-process (program &optional destination &rest args)
> (let ((process (make-process :name "call-process"
> :buffer destination
> :command (cons program args))))
> (while (accept-process-output process))))
>
> my-call-process is missing a few arguments that the real call-process
> has. But if this is all I use, is there *any* reason to *not* use
> my-call-process on Linux?
You are free to do it if it suits your needs. Emacs provides those
primitives to you.
But saying that this should replace call-process in each and every
case is a non-starter.
> There is at least one strong reason to use it: It won't hang other
> processes.
Yes, and gazillion complications, like handling the SIGCHLD signal,
pselect interface, etc.
> > Anyway, this kind of discussion doesn't belong in a bug report about X
> > selections.
>
> But the entire point of this discussion, for me, is to fix the
> X-selection-related hangs which Emacs currently causes when in
> call-process. i.e., this bug report.
It doesn't matter, because you insist on making the issue much more
general.
This bug report was last modified 1 year and 357 days ago.
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