Hi,
I catch a thread deadlock while running H2 database in embedded mode with my
app.
H2 1.4.196, connection string: jdbc:h2:file:mydir/mydb;MAX_MEMORY_ROWS=50000
Found one Java-level deadlock:
=============================
"Thread-102":
waiting to lock monitor 0x00007f10580058e8 (object 0x00000005c9415e30, a
org.h2.engine.Database),
which is held by "Thread-99"
"Thread-99":
waiting to lock monitor 0x00007f0fec0087e8 (object 0x00000005c95fd490, a
org.h2.engine.Session),
which is held by "pool-thread-1"
"pool-thread-1":
waiting to lock monitor 0x00007f10580058e8 (object 0x00000005c9415e30, a
org.h2.engine.Database),
which is held by "Thread-99"
Java stack information for the threads listed above:
===================================================
"Thread-102":
at org.h2.command.Command.executeUpdate(Command.java:253)
- waiting to lock <0x00000005c9415e30> (a org.h2.engine.Database)
at
org.h2.jdbc.JdbcPreparedStatement.executeUpdateInternal(JdbcPreparedStatement.java:164)
- locked <0x00000005ca95fca8> (a org.h2.engine.Session)
at
org.h2.jdbc.JdbcPreparedStatement.executeBatch(JdbcPreparedStatement.java:1215)
...
"Thread-99":
at org.h2.command.ddl.Analyze.analyzeTable(Analyze.java:145)
- waiting to lock <0x00000005c95fd490> (a org.h2.engine.Session)
at org.h2.engine.Session.commit(Session.java:671)
at org.h2.command.dml.TransactionCommand.update(TransactionCommand.java:46)
at org.h2.command.CommandContainer.update(CommandContainer.java:101)
at org.h2.command.Command.executeUpdate(Command.java:260)
- locked <0x00000005c9415e30> (a org.h2.engine.Database)
at org.h2.jdbc.JdbcConnection.commit(JdbcConnection.java:479)
- locked <0x00000005dddbe080> (a
org.h2.jdbcx.JdbcXAConnection$PooledJdbcConnection)
...
"pool-thread-1":
at org.h2.result.ResultTempTable.dropTable(ResultTempTable.java:234)
- waiting to lock <0x00000005c9415e30> (a org.h2.engine.Database)
- locked <0x00000005c95fd490> (a org.h2.engine.Session)
- locked <0x00000005ca914f30> (a org.h2.engine.Session)
at org.h2.result.ResultTempTable.close(ResultTempTable.java:192)
- locked <0x00000005d566e4a8> (a org.h2.result.ResultTempTable)
at org.h2.result.LocalResult.close(LocalResult.java:429)
at org.h2.jdbc.JdbcResultSet.nextRow(JdbcResultSet.java:3274)
at org.h2.jdbc.JdbcResultSet.next(JdbcResultSet.java:131)
...
Found 1 deadlock.
The problem is that Thread-99 and pool-thread-1 locks the Database
<0x00000005c9415e30>
and the SystemSession <0x00000005c95fd490> objects in a different orders.
Thread-99 is making Connection.commit() after a simple INSERT,
pool-thread-1 is finishing to read a large resultset.
In ResultTempTable.java I've found a potential problem: probably the
synchronization cascade must be reordered.
// the transaction must be committed immediately
// TODO this synchronization cascade is very ugly
synchronized (session) {
synchronized (sysSession) {
synchronized (database) {
sysSession.commit(false);
}
}
}
Best regards,
Antón
--
You received this message because you are subscribed to the Google Groups "H2
Database" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/h2-database.
For more options, visit https://groups.google.com/d/optout.
