calling this done.. hopefully

diff --git a/doc/bugs/locking_fun.mdwn b/doc/bugs/locking_fun.mdwn
index 64d06917f3022ac41276ace5f8c9b31ea8612349..46278b0283030ccc8f2a452bc6c106b0c57480f1 100644 (file)
--- a/doc/bugs/locking_fun.mdwn
+++ b/doc/bugs/locking_fun.mdwn
@@ -7,6 +7,8 @@ This can happen because CGI.pm writes the change, then drops the main wiki
 lock before calling rcs_commit. It can't keep the lock because the commit
 hook needs to be able to lock.
 
 lock before calling rcs_commit. It can't keep the lock because the commit
 hook needs to be able to lock.
 

+-------
+

 We batted this around for an hour or two on irc. The best solution seems to
 be adding a subsidiary second lock, which is only used to lock the working
 copy and is a blocking read/write lock.
 We batted this around for an hour or two on irc. The best solution seems to
 be adding a subsidiary second lock, which is only used to lock the working
 copy and is a blocking read/write lock.


@@ -34,103 +36,7 @@ original race. It should be possible though to use a separate exclusive lock,
 wrapped around these flock calls, to force them to be "atomic" and avoid that
 race.
 
 wrapped around these flock calls, to force them to be "atomic" and avoid that
 race.
 

-Sample patch, with stub functions for the new lock:
-
-[[toggle text="expand patch"]]
-[[toggleable text="""
-<pre>
-Index: IkiWiki/CGI.pm
-===================================================================
---- IkiWiki/CGI.pm     (revision 2774)
-+++ IkiWiki/CGI.pm     (working copy)
-@@ -494,9 +494,14 @@
-               $content=~s/\r\n/\n/g;
-               $content=~s/\r/\n/g;
- 
-+              lockwc_exclusive();
-+
-               $config{cgi}=0; # avoid cgi error message
-               eval { writefile($file, $config{srcdir}, $content) };
-               $config{cgi}=1;
-+
-+              lockwc_shared();
-+
-               if ($@) {
-                       $form->field(name => "rcsinfo", value => rcs_prepedit($file),
-                               force => 1);
-Index: IkiWiki/Plugin/poll.pm
-===================================================================
---- IkiWiki/Plugin/poll.pm     (revision 2770)
-+++ IkiWiki/Plugin/poll.pm     (working copy)
-@@ -120,7 +120,9 @@
-               $content =~ s{(\\?)\[\[poll\s+([^]]+)\s*\]\]}{$edit->($1, $2)}seg;
- 
-               # Store their vote, update the page, and redirect to it.
-+              IkiWiki::lockwc_exclusive();
-               writefile($pagesources{$page}, $config{srcdir}, $content);
-+              IkiWiki::lockwc_shared();
-               $session->param($choice_param, $choice);
-               IkiWiki::cgi_savesession($session);
-               $oldchoice=$session->param($choice_param);
-@@ -130,6 +132,10 @@
-                       IkiWiki::rcs_commit($pagesources{$page}, "poll vote ($choice)",
-                               IkiWiki::rcs_prepedit($pagesources{$page}),
-                               $session->param("name"), $ENV{REMOTE_ADDR});
-+                      # Make sure that the repo is up-to-date;
-+                      # locking prevents the post-commit hook
-+                      # from updating it.
-+                      rcs_update();
-               }
-               else {
-                       require IkiWiki::Render;
-Index: ikiwiki.in
-===================================================================
---- ikiwiki.in (revision 2770)
-+++ ikiwiki.in (working copy)
-@@ -121,6 +121,7 @@
-               lockwiki();
-               loadindex();
-               require IkiWiki::Render;
-+              lockwc_shared();
-               rcs_update();
-               refresh();
-               rcs_notify() if $config{notify};
-Index: IkiWiki.pm
-===================================================================
---- IkiWiki.pm (revision 2770)
-+++ IkiWiki.pm (working copy)
-@@ -617,6 +617,29 @@
-       close WIKILOCK;
- } #}}}
- 
-+sub lockwc_exclusive () { #{{{
-+      # Take an exclusive lock on the working copy.
-+      # The lock will be dropped on program exit.
-+      # Note: This lock should only be taken _after_ the main wiki
-+      # lock.
-+      
-+      # TODO
-+} #}}}
-+
-+sub lockwc_shared () { #{{{
-+      # Take a shared lock on the working copy. If an exclusive lock
-+      # already exists, downgrade it to a shared lock.
-+      # The lock will be dropped on program exit.
-+      # Note: This lock should only be taken _after_ the main wiki
-+      # lock.
-+      
-+      # TODO
-+} #}}}
-+
-+sub unlockwc () { #{{{
-+      close WIKIWCLOCK;
-+} #}}}
-+
- sub loadindex () { #{{{
-       open (IN, "$config{wikistatedir}/index") || return;
-       while (<IN>) {
-</pre>
-"""]]
+------

 
 My alternative idea, which seems simpler than all this tricky locking
 stuff, is to introduce a new lock file (really a flag file implemented
 
 My alternative idea, which seems simpler than all this tricky locking
 stuff, is to introduce a new lock file (really a flag file implemented


@@ -190,3 +96,10 @@ The commit hook takes them in the order (wclock, wikilock). This is a
 classic potential deadlock scenario. _However_, the commit hook should
 close the wclock as soon as it successfully opens it, before taking the
 wikilock, so I think that's ok.
 classic potential deadlock scenario. _However_, the commit hook should
 close the wclock as soon as it successfully opens it, before taking the
 wikilock, so I think that's ok.

+
+-----
+
+I've committed an implementation of my idea just above, and it seems to
+work, although testing for races etc is tricky. Calling this [[bugs/done]]
+unless someone finds a new bug or finds a problem in my thinking above.
+--[[Joey]]