AW: AW: AW: Can't interrupt directory_files_internalrunfromtimer-event-handler

AW: AW: AW: Can't interrupt directory_files_internalrunfromtimer-event-handler

[klaus.berndl]

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>>    >The best way to do this and make sure it is stealthy is by running a
>>    >subprocess.  The subprocess can run in parallel with Emacs.

>>    Hmm, i'm not sure if this is the best way?!

>If the primitives you need to do the job in Emacs LIsp can be slow, I
>see no other way to do the job except to avoid using those primitives.

I see another way:

IMHO reinventing the wheel for all these (potentially slow) elisp-
primitives is not worth the effort because IMHO for an ECB-user it is
much more important not being blocked. This can be achieved much easier
by implementing the stealthy task so they each key- or mouse-press
immediatelly interrupts a long-lasting action. So i do not really
elisp-threads if there is at least a elisp-tool which guarantees this
interrupt. AFAIK while-no-input is this tool . The only disadvantage
i can see is that it will be first available in Emacs 22. Therefore
my other question in another answer for with-local-quit mentioned by
Stefan (he said, this could be easily backported). AFAICS with-local-quit
would at least guarantee that C-g interrupts a long-lasting iteration
of a stealth task, right?

>Some day maybe that Emacs will have multi-threading, but that
>won't be soon.

I will not stop breathing until this feature will arise ;-)

Thansk for your help
Klaus

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Re: AW: AW: AW: Can't interrupt directory_files_internalrunfromtimer-event-handler

[Richard M. Stallman]

I looked at the code for directory-files, and it seems you cannot quit
out of it while it is waiting in a system call.  This means that
while-no-input won't currently work when directory-files hangs in that
way.

It is probably possible to implement quitting out of the system call
in directory-files.  Doing this requires setting immediate_quit to 1,
at least while that system call is running.

Which system call takes the long time?  Is it opendir, or readdir?

Re: AW: AW: AW: Can't interrupt directory_files_internalrunfromtimer-event-handler

[Stefan Monnier]

> I looked at the code for directory-files, and it seems you cannot quit
> out of it while it is waiting in a system call.

Why is that?

> It is probably possible to implement quitting out of the system call
> in directory-files.  Doing this requires setting immediate_quit to 1,
> at least while that system call is running.

Looking at this code made me notice that the filename completion doesn't
handle the EAGAIN case like directory-files does.  And also that
directory-files doesn't check QUIT if it had been interrupted, which can
fail to react to C-g in cases such as SYNC_INPUT.
So I've installed the patch below.

> Which system call takes the long time?  Is it opendir, or readdir?

If the NFS server is down, I suspect that either call can stall.


        Stefan


--- dired.c	11 aoû 2005 05:27:35 -0400	1.117
+++ dired.c	14 aoû 2005 02:44:01 -0400	
@@ -224,7 +224,7 @@
 
 #ifdef EAGAIN
       if (dp == NULL && errno == EAGAIN)
-	continue;
+	{ QUIT; continue; }
 #endif
 
       if (dp == NULL)
@@ -533,6 +533,10 @@
 	  dp = (*readfunc) (d);
 #else
 	  dp = readdir (d);
+#endif
+#ifdef EAGAIN
+	  if (dp == NULL && errno == EAGAIN)
+	    { QUIT; continue; }
 #endif
 	  if (!dp) break;