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<channel>
    <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>
    </build-info>


<item>
            <title>[SERVER-19947] Deadlock between aggregations with sorts on sharded collections and operations requiring MODE_X database locks</title>
                <link>https://jira.mongodb.org/browse/SERVER-19947</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;This is a deadlock that occurs when a shard is trying to receive a chunk while also acting as the merge node for an aggregation sort. There are three threads in one process involved.&lt;/p&gt;

&lt;p&gt;Thread 1 is servicing a getmore request for an aggregation pipeline. A relevant portion of its stack frame is below:&lt;/p&gt;

&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#7  0x000000000159bf52 in mongo::MessagingPort::recv (this=0x6f5fe40, toSend=..., response=...) at src/mongo/util/net/message_port.cpp:227&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#8  0x000000000159c2e5 in mongo::MessagingPort::call (this=&amp;lt;optimized out&amp;gt;, toSend=..., response=...) at src/mongo/util/net/message_port.cpp:222&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#9  0x0000000000d7921f in mongo::DBClientConnection::call (this=0x3c77c20, toSend=..., response=..., assertOk=&amp;lt;optimized out&amp;gt;, &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    actualServer=&amp;lt;optimized out&amp;gt;) at src/mongo/client/dbclient.cpp:1478&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#10 0x0000000000d8b7dc in mongo::DBClientCursor::requestMore (this=this@entry=0x3bcc648) at src/mongo/client/dbclientcursor.cpp:210&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#11 0x0000000000d8bcc7 in mongo::DBClientCursor::more (this=0x3bcc648) at src/mongo/client/dbclientcursor.cpp:341&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#12 0x00000000010adf73 in mongo::sorter::MergeIterator&amp;lt;mongo::Value, mongo::Document, mongo::DocumentSourceSort::Comparator&amp;gt;::next() ()&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#13 0x00000000010aa611 in mongo::DocumentSourceSort::getNext (this=&amp;lt;optimized out&amp;gt;) at src/mongo/db/pipeline/document_source_sort.cpp:71&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#14 0x0000000000f59740 in mongo::PipelineProxyStage::getNextBson (this=this@entry=0x3c75840) at src/mongo/db/exec/pipeline_proxy.cpp:131&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#15 0x0000000000f5a34f in mongo::PipelineProxyStage::isEOF (this=0x3c75840) at src/mongo/db/exec/pipeline_proxy.cpp:87&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#16 0x0000000001107e84 in mongo::shouldSaveCursorGetMore (finalState=&amp;lt;optimized out&amp;gt;, exec=exec@entry=0x3c75920, isTailable=&amp;lt;optimized out&amp;gt;)&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/mongo/db/query/find.cpp:122&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#17 0x0000000001108e6d in mongo::getMore (txn=txn@entry=0x7fffe7a02bd0, ns=ns@entry=0x3c7b5e4 &quot;aggShard.server9444&quot;, ntoreturn=ntoreturn@entry=0, &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    cursorid=cursorid@entry=35834991707, exhaust=exhaust@entry=0x7fffe7a01fbd, isCursorAuthorized=isCursorAuthorized@entry=0x7fffe7a01fbe)&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/mongo/db/query/find.cpp:414&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;We can see that thread 1 is blocked because shouldSaveGetMore has asked its pipeline to answer the predicate isEOF, and the PipelineProxy stage has turned that into a getNext(), which in turn causes the sorter to fetch data on one of its remote cursors. At this point, thread 1 holds the database lock for the source of the aggregation in MODE_IS. Notably, the &quot;remote cursor&quot; is actually in the same process; the stack frames near the top are engaging the network layer to communicate with this very process on another thread.&lt;/p&gt;

&lt;p&gt;At this point, thread 2 starts the migrate thread driver run by the recipients of new chunks. The other shard in this cluster (not pictured) has started donated a new chunk to this node, coincidentally on the same database as the one the agg is running on. Thread 2 blocks trying to acquire the database lock in MODE_X, because thread 1 has it in MODE_IS. Stack trace is below.&lt;/p&gt;

&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#13 0x0000000000f00cf7 in mongo::Lock::DBLock::DBLock (this=0x7fffd7602c10, locker=0x3c7b9e0, db=..., mode=&amp;lt;optimized out&amp;gt;)&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/mongo/db/concurrency/d_concurrency.cpp:110&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#14 0x00000000012970f1 in mongo::MigrationDestinationManager::_migrateDriver (&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    this=this@entry=0x1ffbbc0 &amp;lt;mongo::(anonymous namespace)::migrateDestManager&amp;gt;, txn=txn@entry=0x7fffd7602e10, ns=..., min=..., max=..., &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    shardKeyPattern=..., fromShard=..., epoch=..., writeConcern=...) at src/mongo/db/s/migration_destination_manager.cpp:434&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;Now, thread 3 starts trying to process the getmore requested issued to it from thread 1. It attempts to acquire the same database lock as threads 1 and 2 in MODE_IS. However, since thread 2 is waiting in MODE_X, it prevents any new threads from acquiring in MODE_IS. We are now deadlocked.  Here&apos;s thread 3&apos;s stack:&lt;/p&gt;

&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#13 0x0000000000f00cf7 in mongo::Lock::DBLock::DBLock (this=0x648b430, locker=0x3bf1e00, db=..., mode=&amp;lt;optimized out&amp;gt;)&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/mongo/db/concurrency/d_concurrency.cpp:110&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#14 0x0000000001108e12 in make_unique&amp;lt;mongo::Lock::DBLock, mongo::Locker*, mongo::StringData, mongo::LockMode&amp;gt; ()&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/third_party/boost-1.56.0/boost/smart_ptr/make_unique_object.hpp:28&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#15 mongo::getMore (txn=txn@entry=0x7ffff2ffbbd0, ns=ns@entry=0x5cf1084 &quot;aggShard.server9444&quot;, ntoreturn=ntoreturn@entry=0, &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    cursorid=cursorid@entry=36214372988, exhaust=exhaust@entry=0x7ffff2ffafbd, isCursorAuthorized=isCursorAuthorized@entry=0x7ffff2ffafbe)&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    at src/mongo/db/query/find.cpp:404&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;Relevant build failures:&lt;br/&gt;
&lt;a href=&quot;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_aa82208d53a4b642441adbadd4bd0595c4fa40ae_15_08_11_21_38_16&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_aa82208d53a4b642441adbadd4bd0595c4fa40ae_15_08_11_21_38_16&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_8e2990da71c1498d2a979ef47c07c2bfc2fa4f97_15_08_11_15_05_28&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_8e2990da71c1498d2a979ef47c07c2bfc2fa4f97_15_08_11_15_05_28&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_a067d03eca22d67a1ca036ea61544cd51df1490b_15_08_10_21_57_24&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_a067d03eca22d67a1ca036ea61544cd51df1490b_15_08_10_21_57_24&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_55f6c3a09f96aabe7c933d9262cf011c7776fd60_15_08_10_12_56_20&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://evergreen.mongodb.com/task/mongodb_mongo_master_solaris_64_bit_aggregation_55f6c3a09f96aabe7c933d9262cf011c7776fd60_15_08_10_12_56_20&lt;/a&gt;&lt;/p&gt;</description>
                <environment></environment>
        <key id="225216">SERVER-19947</key>
            <summary>Deadlock between aggregations with sorts on sharded collections and operations requiring MODE_X database locks</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="9">Done</resolution>
                                        <assignee username="david.storch@mongodb.com">David Storch</assignee>
                                    <reporter username="atul.kachru">Atul Kachru</reporter>
                        <labels>
                    </labels>
                <created>Wed, 12 Aug 2015 04:26:03 +0000</created>
                <updated>Sat, 19 Sep 2015 00:09:31 +0000</updated>
                            <resolved>Mon, 17 Aug 2015 20:49:22 +0000</resolved>
                                                    <fixVersion>3.1.7</fixVersion>
                                    <component>Aggregation Framework</component>
                    <component>Querying</component>
                                        <votes>0</votes>
                                    <watches>6</watches>
                                                                                                                <comments>
                            <comment id="1007512" author="xgen-internal-githook" created="Mon, 17 Aug 2015 20:48:19 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;dstorch&apos;, u&apos;name&apos;: u&apos;David Storch&apos;, u&apos;email&apos;: u&apos;david.storch@10gen.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-19947&quot; title=&quot;Deadlock between aggregations with sorts on sharded collections and operations requiring MODE_X database locks&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-19947&quot;&gt;&lt;del&gt;SERVER-19947&lt;/del&gt;&lt;/a&gt; fix distributed deadlock by preventing agg cursors from making a network call from inside the collection lock&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/b4f7738e808361c3edc0c040d8eb560b7f6f1526&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/b4f7738e808361c3edc0c040d8eb560b7f6f1526&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1007362" author="david.storch" created="Mon, 17 Aug 2015 18:16:21 +0000"  >&lt;p&gt;We&apos;ve had this bug before: it was fixed under &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18203&quot; title=&quot;Aggregation distributed deadlock with sharding&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18203&quot;&gt;&lt;del&gt;SERVER-18203&lt;/del&gt;&lt;/a&gt;, and then regressed again in &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18841&quot; title=&quot;Make awaitData cursors block rather than busy wait in the OP_GET_MORE path&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18841&quot;&gt;&lt;del&gt;SERVER-18841&lt;/del&gt;&lt;/a&gt;. This makes me think that we should consider scheduling &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-17839&quot; title=&quot;Remove PlanStage::isEOF&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-17839&quot;&gt;SERVER-17839&lt;/a&gt;: this work would offer a much more stable fix that is unlikely to be broken by unrelated refactoring.&lt;/p&gt;</comment>
                            <comment id="1005190" author="schwerin" created="Thu, 13 Aug 2015 23:28:32 +0000"  >&lt;p&gt;This is exercised regularly by our Solaris builder in Evergreen, but nothing about this bug is specific to Solaris.&lt;/p&gt;</comment>
                            <comment id="1005186" author="schwerin" created="Thu, 13 Aug 2015 23:25:15 +0000"  >&lt;p&gt;I believe the true problem here is that thread 1 in the description should not be doing network work inside of isEOF. It&apos;s extra bad that it&apos;s calling itself, but going to the network while holding a lock is pretty much forbidden. In addition to the risk of distributed deadlock, it can prevent other threads from getting locks in a timely manner.&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
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                                                                <inwardlinks description="is related to">
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            <issuekey id="195985">SERVER-18203</issuekey>
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            <issuekey id="193396">SERVER-17839</issuekey>
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