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        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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            <title>[SERVER-56768] Race in atomic compareAndSwap can make FailPoint::enableFailPoint() to spin forever</title>
                <link>https://jira.mongodb.org/browse/SERVER-56768</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;This is not a production bug so threat it accordingly.&lt;/p&gt;

&lt;p&gt;The race:&lt;br/&gt;
Initially, _fpInfo was ( 1 &amp;lt;&amp;lt; 31 ).&lt;br/&gt;
1. Thread 1 enters &lt;a href=&quot;https://github.com/mongodb/mongo/blob/23334d09cd768898b6524cfe6499d7d036f20d21/src/mongo/util/fail_point.cpp#L148&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;FailPoint::slowShouldFailOpenBlock()&lt;/a&gt; and increments the _fpInfo to ( 1 &amp;lt;&amp;lt; 31 + 1)&lt;br/&gt;
2. Thread 2 enters disableFailPoint() and reads _fpInfo into currentVal&lt;br/&gt;
3. Thread 1 enters FailPoint::shouldFailCloseBlock() and decrements _fpInfo to ( 1 &amp;lt;&amp;lt; 31 ) &lt;br/&gt;
4. Thread 2 spins forever&lt;/p&gt;

&lt;p&gt;Even though this is not production failure, someone may copy-paste this pattern into production code. Atomics are subtle and must be treated with care.&lt;/p&gt;

&lt;p&gt;Fix: load _fpInfo each time inside loop. Same for enableFailPoint().&lt;/p&gt;</description>
                <environment></environment>
        <key id="1706948">SERVER-56768</key>
            <summary>Race in atomic compareAndSwap can make FailPoint::enableFailPoint() to spin forever</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="1" iconUrl="https://jira.mongodb.org/images/icons/statuses/open.png" description="">Open</status>
                    <statusCategory id="2" key="new" colorName="default"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="backlog-server-servicearch">Backlog - Service Architecture</assignee>
                                    <reporter username="andrew.shuvalov@mongodb.com">Andrew Shuvalov</reporter>
                        <labels>
                    </labels>
                <created>Fri, 7 May 2021 18:22:06 +0000</created>
                <updated>Tue, 6 Dec 2022 01:19:31 +0000</updated>
                                            <version>4.0.24</version>
                                    <fixVersion>4.0 Required</fixVersion>
                                                        <votes>0</votes>
                                    <watches>1</watches>
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