GNU bug report logs - #44639
[PATCH 2/2] autorevert: map each watch descriptor to a single buffer

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Spencer Baugh <sbaugh <at> catern.com>
To: bug-gnu-emacs <at> gnu.org
Cc: Spencer Baugh <sbaugh <at> catern.com>
Subject: [PATCH 2/2] autorevert: map each watch descriptor to a single buffer
Date: Sat, 14 Nov 2020 11:54:59 -0500

Now that we don't share watch descriptors between buffers, we don't
need to store a list of buffers for each watch descriptor - there
would only be a single buffer in each list. This should have no
functional change.
---
 lisp/autorevert.el | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/lisp/autorevert.el b/lisp/autorevert.el
index d5bb75c2f1..ad39884ab0 100644
--- a/lisp/autorevert.el
+++ b/lisp/autorevert.el
@@ -355,10 +355,10 @@ the list of old buffers.")
 (add-hook 'after-set-visited-file-name-hook
           #'auto-revert-set-visited-file-name)
 
-(defvar auto-revert--buffers-by-watch-descriptor
+(defvar auto-revert--buffer-by-watch-descriptor
   (make-hash-table :test 'equal)
-  "A hash table mapping notification descriptors to lists of buffers.
-The buffers use that descriptor for auto-revert notifications.
+  "A hash table mapping notification descriptors to buffers.
+The buffer uses that descriptor for auto-revert notifications.
 The key is equal to `auto-revert-notify-watch-descriptor' in each
 buffer.")
 
@@ -631,12 +631,9 @@ will use an up-to-date value of `auto-revert-interval'."
 (defun auto-revert-notify-rm-watch ()
   "Disable file notification for current buffer's associated file."
   (let ((desc auto-revert-notify-watch-descriptor)
-        (table auto-revert--buffers-by-watch-descriptor))
+        (table auto-revert--buffer-by-watch-descriptor))
     (when desc
-      (let ((buffers (delq (current-buffer) (gethash desc table))))
-        (if buffers
-            (puthash desc buffers table)
-          (remhash desc table)))
+      (remhash desc table)
       (ignore-errors
 	(file-notify-rm-watch desc))
       (remove-hook 'kill-buffer-hook #'auto-revert-notify-rm-watch t)))
@@ -663,10 +660,8 @@ will use an up-to-date value of `auto-revert-interval'."
         (setq auto-revert-notify-modified-p t)
         (puthash
          auto-revert-notify-watch-descriptor
-         (cons (current-buffer)
-	       (gethash auto-revert-notify-watch-descriptor
-		        auto-revert--buffers-by-watch-descriptor))
-         auto-revert--buffers-by-watch-descriptor)
+         (current-buffer)
+         auto-revert--buffer-by-watch-descriptor)
         (add-hook 'kill-buffer-hook #'auto-revert-notify-rm-watch nil t))))
 
 ;; If we have file notifications, we want to update the auto-revert buffers
@@ -696,8 +691,8 @@ system.")
 	   (action (nth 1 event))
 	   (file (nth 2 event))
 	   (file1 (nth 3 event)) ;; Target of `renamed'.
-	   (buffers (gethash descriptor
-			     auto-revert--buffers-by-watch-descriptor)))
+	   (buffer (gethash descriptor
+			    auto-revert--buffer-by-watch-descriptor)))
       ;; Check, that event is meant for us.
       (cl-assert descriptor)
       ;; Since we watch a directory, a file name must be returned.
@@ -708,7 +703,6 @@ system.")
 
       (if (eq action 'stopped)
           ;; File notification has stopped.  Continue with polling.
-          (cl-dolist (buffer buffers)
             (with-current-buffer buffer
               (when (or
                      ;; A buffer associated with a file.
@@ -721,10 +715,8 @@ system.")
                 (auto-revert-notify-rm-watch)
                 ;; Restart the timer if it wasn't running.
                 (unless auto-revert-timer
-                  (auto-revert-set-timer)))))
+                  (auto-revert-set-timer))))
 
-        ;; Loop over all buffers, in order to find the intended one.
-        (cl-dolist (buffer buffers)
           (when (buffer-live-p buffer)
             (with-current-buffer buffer
               (when (or
@@ -752,7 +744,7 @@ system.")
                   (setq auto-revert--lockout-timer
                         (run-with-timer
                          auto-revert--lockout-interval nil
-                         #'auto-revert--end-lockout buffer)))))))))))
+                         #'auto-revert--end-lockout buffer))))))))))
 
 (defun auto-revert--end-lockout (buffer)
   "End the lockout period after a notification.
-- 
2.28.0

Message #8 received at 44639 <at> debbugs.gnu.org (full text, mbox):

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Spencer Baugh <sbaugh <at> catern.com>
Cc: 44639 <at> debbugs.gnu.org
Subject: Re: bug#44639: [PATCH 2/2] autorevert: map each watch descriptor to
 a single buffer
Date: Wed, 02 Dec 2020 15:50:16 +0100

Spencer Baugh <sbaugh <at> catern.com> writes:

> Now that we don't share watch descriptors between buffers, we don't
> need to store a list of buffers for each watch descriptor - there
> would only be a single buffer in each list. This should have no
> functional change.

Just for the records, when I apply both patches 1/2 and 2/2,
autorevert-tests fails. So it cannot be applied as such.

Using just patch 1/2 works for the inotify backend. I'll continue to
test. I recommend you to test also your patches by calling

$ make -C test autorevert-tests

Best regards, Michael.

Message #11 received at 44639 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Michael Albinus <michael.albinus <at> gmx.de>
Cc: Spencer Baugh <sbaugh <at> catern.com>, 44639 <at> debbugs.gnu.org
Subject: Re: bug#44639: [PATCH 2/2] autorevert: map each watch descriptor to
 a single buffer
Date: Wed, 27 Jan 2021 04:59:05 +0100

Michael Albinus <michael.albinus <at> gmx.de> writes:

> Spencer Baugh <sbaugh <at> catern.com> writes:
>
>> Now that we don't share watch descriptors between buffers, we don't
>> need to store a list of buffers for each watch descriptor - there
>> would only be a single buffer in each list. This should have no
>> functional change.
>
> Just for the records, when I apply both patches 1/2 and 2/2,
> autorevert-tests fails. So it cannot be applied as such.

Spencer, did you do any further work on this patch?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #16 received at 44639 <at> debbugs.gnu.org (full text, mbox):

From: Spencer Baugh <sbaugh <at> catern.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>, Michael Albinus
 <michael.albinus <at> gmx.de>
Cc: 44639 <at> debbugs.gnu.org
Subject: Re: bug#44639: [PATCH 2/2] autorevert: map each watch descriptor to
 a single buffer
Date: Wed, 27 Jan 2021 11:34:01 -0500

Lars Ingebrigtsen <larsi <at> gnus.org> writes:
> Michael Albinus <michael.albinus <at> gmx.de> writes:
>
>> Spencer Baugh <sbaugh <at> catern.com> writes:
>>
>>> Now that we don't share watch descriptors between buffers, we don't
>>> need to store a list of buffers for each watch descriptor - there
>>> would only be a single buffer in each list. This should have no
>>> functional change.
>>
>> Just for the records, when I apply both patches 1/2 and 2/2,
>> autorevert-tests fails. So it cannot be applied as such.
>
> Spencer, did you do any further work on this patch?

Not this patch, no.  Locally I have applied patch 1/2 and not patch
2/2. Patch 2/2 just removes dead code after patch 1/2 removes the
functionality, and I must have gotten it wrong.

But I can report that performance has been fine with patch 1/2 - I
haven't seen the pathological case I was seeing before, and I haven't
seen any new pathological cases to replace it.

Message #19 received at 44639 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Spencer Baugh <sbaugh <at> catern.com>
Cc: Michael Albinus <michael.albinus <at> gmx.de>, 44639 <at> debbugs.gnu.org
Subject: Re: bug#44639: [PATCH 2/2] autorevert: map each watch descriptor to
 a single buffer
Date: Thu, 28 Jan 2021 04:29:16 +0100

Spencer Baugh <sbaugh <at> catern.com> writes:

>>> Just for the records, when I apply both patches 1/2 and 2/2,
>>> autorevert-tests fails. So it cannot be applied as such.
>>
>> Spencer, did you do any further work on this patch?
>
> Not this patch, no.  Locally I have applied patch 1/2 and not patch
> 2/2. Patch 2/2 just removes dead code after patch 1/2 removes the
> functionality, and I must have gotten it wrong.
>
> But I can report that performance has been fine with patch 1/2 - I
> haven't seen the pathological case I was seeing before, and I haven't
> seen any new pathological cases to replace it.

Patch 1/2 was applied to Emacs 28 some time ago (and works fine), so
this was just a followup on 2/2 -- whether this clean-up patch (which
apparently doesn't work correctly, according to Michael) is going to get
any further work done, or whether this issue should just be closed...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #24 received at 44639-done <at> debbugs.gnu.org (full text, mbox):

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: Spencer Baugh <sbaugh <at> catern.com>, 44639-done <at> debbugs.gnu.org
Subject: Re: bug#44639: [PATCH 2/2] autorevert: map each watch descriptor to
 a single buffer
Date: Thu, 28 Jan 2021 15:19:33 +0100

[Message part 1 (text/plain, inline)]

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

Hi,

> Patch 1/2 was applied to Emacs 28 some time ago (and works fine), so
> this was just a followup on 2/2 -- whether this clean-up patch (which
> apparently doesn't work correctly, according to Michael) is going to get
> any further work done, or whether this issue should just be closed...

I've reworked the patch, using an association list instead of a hash
table. By this, I've fixed also the error which was always evident, but
uncovered only by Spencer's patch.

Pushed to master, I'm closing the bug. The patch itself is appended
below.

Best regards, Michael.

[Message part 2 (text/x-patch, attachment)]

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