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 h2-database+unsubscr...@googlegroups.com.
To post to this group, send email to h2-database@googlegroups.com.
Visit this group at https://groups.google.com/group/h2-database.
For more options, visit https://groups.google.com/d/optout.
