'Re: Review Request 111718: Prevent EntityListCache from causing endless loop'

[prev in list] [next in list] [prev in thread] [next in thread] 

List:       kde-release-team
Subject:    Re: Review Request 111718: Prevent EntityListCache from causing endless loop
From:       "Commit Hook" <null () kde ! org>
Date:       2013-07-27 12:04:23
Message-ID: 20130727120423.4847.22843 () vidsolbach ! de
[Download RAW message or body]

[Attachment #2 (multipart/alternative)]

-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/111718/
-----------------------------------------------------------

(Updated July 27, 2013, 12:04 p.m.)

Status
------

This change has been marked as submitted.

Review request for KDEPIM-Libraries and Release Team.

Description
-------

Calling ensureCached() can cause the cache and Monitor to end up in an endless loop.

In situation, that there are items 1,2,4,5 and 6 in the cache, calling ensureCached(1,2,3,4,5) will call \
request(3) and return false. request() internally calls shrinkCache() which removes all fetched items to \
make sure the cache does not grow indefinitely. After the item 3 is fetched, we end up with cache with \
only item 3. Monitor will then again call ensureCached(1,2,3,4,5), which will call request(1,2,4,5) which \
in return calls shrinkCache(), which will remove the item 3 and after fetched is finished the cache only \
contains items 1,2,4 and 5. This way the cache ends up in an endless loop because it will never contain \
all items that Monitor requested.

This patch prevents shrinkCache() from removing items that are part of the ensureCached() request.

I would like to get this patch to 4.11, because it's not that difficult to trigger this bug and in such \
case you end up with Akonadi resource going nuts (and not processing any further requests)

This implementation is still not optimal, because meanwhile the Monitor can call ensureCached(7,8,9), \
which will cause (1,2,4,5) to be removed from cache anyway, so it can take several tries for \
EntityListCache to retrieve the entire set (1,2,3,4,5). However now it's guaranteed that at some point \
the cache will succeed. We can rethink (and maybe remove) the cache when server-side recording is \
implemented.

Diffs
-----

  akonadi/entitycache_p.h 5f00917 

Diff: http://git.reviewboard.kde.org/r/111718/diff/

Testing
-------

Thanks,

Dan Vrátil

[Attachment #5 (text/html)]

<html>
 <body>
  <div style="font-family: Verdana, Arial, Helvetica, Sans-Serif;">
   <table bgcolor="#f9f3c9" width="100%" cellpadding="8" style="border: 1px #c9c399 solid;">
    <tr>
     <td>
      This is an automatically generated e-mail. To reply, visit:
      <a href="http://git.reviewboard.kde.org/r/111718/">http://git.reviewboard.kde.org/r/111718/</a>
     </td>
    </tr>
   </table>
   <br />

<table bgcolor="#e0e0e0" width="100%" cellpadding="8" style="border: 1px gray solid;">
 <tr>
  <td>
   <h1 style="margin-right: 0.2em; padding: 0; font-size: 10pt;">This change has been marked as \
submitted.</h1>  </td>
 </tr>
</table>
<br />

<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" style="background-image: \
url('http://git.reviewboard.kde.org/static/rb/images/review_request_box_top_bg.ab6f3b1072c9.png'); \
background-position: left top; background-repeat: repeat-x; border: 1px black solid;">  <tr>
  <td>

<div>Review request for KDEPIM-Libraries and Release Team.</div>
<div>By Dan Vrátil.</div>

<p style="color: grey;"><i>Updated July 27, 2013, 12:04 p.m.</i></p>

<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
 <table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid \
#b8b5a0">  <tr>
  <td>
   <pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Calling ensureCached() can cause the cache \
and Monitor to end up in an endless loop.

In situation, that there are items 1,2,4,5 and 6 in the cache, calling ensureCached(1,2,3,4,5) will call \
request(3) and return false. request() internally calls shrinkCache() which removes all fetched items to \
make sure the cache does not grow indefinitely. After the item 3 is fetched, we end up with cache with \
only item 3. Monitor will then again call ensureCached(1,2,3,4,5), which will call request(1,2,4,5) which \
in return calls shrinkCache(), which will remove the item 3 and after fetched is finished the cache only \
contains items 1,2,4 and 5. This way the cache ends up in an endless loop because it will never contain \
all items that Monitor requested.

This patch prevents shrinkCache() from removing items that are part of the ensureCached() request.

I would like to get this patch to 4.11, because it&#39;s not that difficult to trigger this bug and in \
such case you end up with Akonadi resource going nuts (and not processing any further requests)

This implementation is still not optimal, because meanwhile the Monitor can call ensureCached(7,8,9), \
which will cause (1,2,4,5) to be removed from cache anyway, so it can take several tries for \
EntityListCache to retrieve the entire set (1,2,3,4,5). However now it&#39;s guaranteed that at some \
point the cache will succeed. We can rethink (and maybe remove) the cache when server-side recording is \
implemented.</pre>  </td>
 </tr>
</table>

<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">

 <li>akonadi/entitycache_p.h <span style="color: grey">(5f00917)</span></li>

</ul>

<p><a href="http://git.reviewboard.kde.org/r/111718/diff/" style="margin-left: 3em;">View Diff</a></p>

  </td>
 </tr>
</table>

  </div>
 </body>
</html>

_______________________________________________
release-team mailing list
release-team@kde.org
https://mail.kde.org/mailman/listinfo/release-team

[prev in list] [next in list] [prev in thread] [next in thread] 