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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-73218] Deadlock among RecoverRefreshThread, index build, step down, and prepared transaction</title>
                <link>https://jira.mongodb.org/browse/SERVER-73218</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;A prepared transaction holds an IX lock on its collection. An index build is about to run its second drain phase and &lt;a href=&quot;https://github.com/mongodb/mongo/blob/c01a9da06fb4f103a0b6b4660cd29db23575e464/src/mongo/db/index_builds_coordinator.cpp#L2785-L2788&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;enqueues a collection S lock (behind the prepared transaction) after explicitly unlocking the RSTL&lt;/a&gt;. The &lt;tt&gt;RecoverRefreshThread&lt;/tt&gt; runs, &lt;a href=&quot;https://github.com/mongodb/mongo/blob/056b0578ea08a530dbee00986c0f4a651771628a/src/mongo/db/s/shard_filtering_metadata_refresh.cpp#L387-L394&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;taking the RSTL in IX and (uninterruptiblty) enqueuing a collection IX lock&lt;/a&gt;. (Since the previously enqueued index build collection lock is mode S, this IX lock will queue behind it despite the lock granted to the prepared transaction also being IX.) Then a step down occurs, &lt;a href=&quot;https://github.com/mongodb/mongo/blob/c01a9da06fb4f103a0b6b4660cd29db23575e464/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp#L548-L552&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;enqueueing the RSTL in X mode&lt;/a&gt; behind &lt;tt&gt;RecoverRefreshThread&lt;/tt&gt;. &lt;a href=&quot;https://github.com/mongodb/mongo/blob/056b0578ea08a530dbee00986c0f4a651771628a/src/mongo/db/s/shard_filtering_metadata_refresh.cpp#L373&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;The &lt;tt&gt;RecoverRefreshThread&lt;/tt&gt; is explicitly marked as being killable by step down&lt;/a&gt;, but the lock acquisition is uninterruptible. Thus a four-way deadlock has been reached.&lt;/p&gt;</description>
                <environment></environment>
        <key id="2240841">SERVER-73218</key>
            <summary>Deadlock among RecoverRefreshThread, index build, step down, and prepared transaction</summary>
                <type id="1" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14703&amp;avatarType=issuetype">Bug</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="13201">Fixed</resolution>
                                        <assignee username="jordi.serra-torrens@mongodb.com">Jordi Serra Torrens</assignee>
                                    <reporter username="gregory.noma@mongodb.com">Gregory Noma</reporter>
                        <labels>
                    </labels>
                <created>Mon, 23 Jan 2023 19:04:41 +0000</created>
                <updated>Sun, 29 Oct 2023 21:27:34 +0000</updated>
                            <resolved>Fri, 27 Jan 2023 09:01:27 +0000</resolved>
                                                    <fixVersion>6.3.0-rc0</fixVersion>
                                                        <votes>0</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="5145333" author="xgen-internal-githook" created="Fri, 27 Jan 2023 08:58:57 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Jordi Serra Torrens&apos;, &apos;email&apos;: &apos;jordi.serra-torrens@mongodb.com&apos;, &apos;username&apos;: &apos;jordist&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-73218&quot; title=&quot;Deadlock among RecoverRefreshThread, index build, step down, and prepared transaction&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-73218&quot;&gt;&lt;del&gt;SERVER-73218&lt;/del&gt;&lt;/a&gt; Make shard/db metadata refresh interruptible&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/1c38cfa4a24055d6804a5fac121cddd29b4e8c3a&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/1c38cfa4a24055d6804a5fac121cddd29b4e8c3a&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="5140150" author="JIRAUSER1257318" created="Wed, 25 Jan 2023 16:39:56 +0000"  >&lt;blockquote&gt;&lt;p&gt;Hey, we want to understand why the RecoverRefreshThread is not interruptible.&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;I&apos;d say the only reason was to ensure &lt;a href=&quot;https://github.com/mongodb/mongo/blob/1ad055e4a0028cf4e1745361b1cb1e8423395f08/src/mongo/db/s/shard_filtering_metadata_refresh.cpp#L408&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;this&lt;/a&gt; was always executed to signal that this refresh has finished and new ones can start. In the PR above I propose an alternative approach that does not require uninterruptability.&lt;/p&gt;

&lt;p&gt;Edit: We opted for a simpler approach where we keep the uninterruptible guard but remove the need to acquire the DB/Collection lock under it (it was unnecessary to begin with). Now under the uninterruptible lock guard all we take is a RESOURCE_MUTEX.&lt;/p&gt;</comment>
                            <comment id="5136645" author="JIRAUSER1253362" created="Tue, 24 Jan 2023 16:21:19 +0000"  >&lt;p&gt;Hey, we want to understand why the &lt;tt&gt;RecoverRefreshThread&lt;/tt&gt; is not interruptible.&lt;/p&gt;</comment>
                    </comments>
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            <issuekey id="2188579">SERVER-71444</issuekey>
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