I believe there is a bug in jstests/fsync2.js such that the test hangs and blocks future builds from being scheduled. I believe the problematic code is:

assert.commandWorked( d.runCommand( {fsync:1, lock: 1 } ) );

for ( i=0; i<200; i++) {
    assert.eq(1, db.fsync2.count());
    sleep(1);
}

db.fsync2.save( {x:1} );

As I understand it, once a database is fsync/locked and a write comes in (the save on the last line), all reads and writes are blocked until the fsync/lock is un-done. Since the Mongo shell does safe-mode writes by default, control will never return to the jstest after the .save() line (it will block indefinitely, or at least seems to be doing so).

Possibly related cases:

• SERVER-4243
• SERVER-1423