c = db.c;
c.drop();

for( i = 0; i < 1000; ++i ) {
    c.save( {} );
}
db.getLastError();

s = startParallelShell( "sleep( 1000 ); db.c.drop();" );

c.mapReduce( function() { sleep( 3 ); }, function() {}, { out:{ inline:1 } } );

s();

Mon Aug 13 10:53:21 [conn5] CMD: drop test.c
Mon Aug 13 10:53:21 [conn4]   warning assertion failure false src/mongo/db/clientcursor.cpp 341
0x106c9b395 0x106e6590b 0x106d788ea 0x1071585a1 0x107195355 0x106ab64a9 0x10717819e 0x107179f20 0x10717b380 0x107120cc5 0x10712179b 0x106fe66f2 0x106feb5f0 0x1069006e7 0x106d44563 0x106d45bc0 0x106d45c22 0x106d45c4d 0x106d39e69 0x108b708bf 
Mon Aug 13 10:53:21 [conn5] end connection 127.0.0.1:56302 (1 connection now open)
 0   mongod                              0x0000000106c9b395 _ZN5mongo15printStackTraceERSo + 37
 1   mongod                              0x0000000106e6590b _ZN5mongo10logContextEPKc + 123
 2   mongod                              0x0000000106d788ea _ZN5mongo9wassertedEPKcS1_j + 538
 3   mongod                              0x00000001071585a1 _ZN5mongo12ClientCursorD1Ev + 57
 4   mongod                              0x0000000107195355 _ZNSt8auto_ptrIN5mongo12ClientCursorEED1Ev + 45
 5   mongod                              0x0000000106ab64a9 _ZN5mongo2mr16MapReduceCommand3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb + 12421
 6   mongod                              0x000000010717819e _ZN5mongo12_execCommandEPNS_7CommandERKSsRNS_7BSONObjEiRNS_14BSONObjBuilderEb + 142
 7   mongod                              0x0000000107179f20 _ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb + 4608
 8   mongod                              0x000000010717b380 _ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 1472
 9   mongod                              0x0000000107120cc5 _ZN5mongo11runCommandsEPKcRNS_7BSONObjERNS_5CurOpERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 117
 10  mongod                              0x000000010712179b _ZN5mongo8runQueryERNS_7MessageERNS_12QueryMessageERNS_5CurOpES1_ + 1595
 11  mongod                              0x0000000106fe66f2 _ZN5mongoL13receivedQueryERNS_6ClientERNS_10DbResponseERNS_7MessageE + 418
 12  mongod                              0x0000000106feb5f0 _ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE + 1136
 13  mongod                              0x00000001069006e7 _ZN5mongo16MyMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE + 261
 14  mongod                              0x0000000106d44563 _ZN5mongo3pms9threadRunEPNS_13MessagingPortE + 2275
 15  mongod                              0x0000000106d45bc0 _ZN5boost3_bi5list1INS0_5valueIPN5mongo13MessagingPortEEEEclIPFvS5_ENS0_5list0EEEvNS0_4typeIvEERT_RT0_i + 78
 16  mongod                              0x0000000106d45c22 _ZN5boost3_bi6bind_tIvPFvPN5mongo13MessagingPortEENS0_5list1INS0_5valueIS4_EEEEEclEv + 92
 17  mongod                              0x0000000106d45c4d _ZN5boost6detail11thread_dataINS_3_bi6bind_tIvPFvPN5mongo13MessagingPortEENS2_5list1INS2_5valueIS6_EEEEEEE3runEv + 37
 18  mongod                              0x0000000106d39e69 thread_proxy + 169
 19  libsystem_c.dylib                   0x0000000108b708bf _pthread_start + 335
mongod(71587,0x10aaa0000) malloc: *** error for object 0x7fd7c9d09640: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Mon Aug 13 10:53:21 Got signal: 6 (Abort trap: 6).

Mon Aug 13 10:53:21 Backtrace:
0x106c9b395 0x1068ebb3e 0x108bc4cfa 0 0x108b63a7a 0x108bc284c 0x108911702 0x108911740 0x107158b18 0x107195355 0x106ab64a9 0x10717819e 0x107179f20 0x10717b380 0x107120cc5 0x10712179b 0x106fe66f2 0x106feb5f0 0x1069006e7 0x106d44563 
 0   mongod                              0x0000000106c9b395 _ZN5mongo15printStackTraceERSo + 37
 1   mongod                              0x00000001068ebb3e _ZN5mongo10abruptQuitEi + 446
 2   libsystem_c.dylib                   0x0000000108bc4cfa _sigtramp + 26
 3   ???                                 0x0000000000000000 0x0 + 0
 4   libsystem_c.dylib                   0x0000000108b63a7a abort + 143
 5   libsystem_c.dylib                   0x0000000108bc284c free + 389
 6   libstdc++.6.dylib                   0x0000000108911702 _ZNSs4_Rep10_M_disposeERKSaIcE + 60
 7   libstdc++.6.dylib                   0x0000000108911740 _ZNSsD2Ev + 44
 8   mongod                              0x0000000107158b18 _ZN5mongo12ClientCursorD1Ev + 1456
 9   mongod                              0x0000000107195355 _ZNSt8auto_ptrIN5mongo12ClientCursorEED1Ev + 45
 10  mongod                              0x0000000106ab64a9 _ZN5mongo2mr16MapReduceCommand3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb + 12421
 11  mongod                              0x000000010717819e _ZN5mongo12_execCommandEPNS_7CommandERKSsRNS_7BSONObjEiRNS_14BSONObjBuilderEb + 142
 12  mongod                              0x0000000107179f20 _ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb + 4608
 13  mongod                              0x000000010717b380 _ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 1472
 14  mongod                              0x0000000107120cc5 _ZN5mongo11runCommandsEPKcRNS_7BSONObjERNS_5CurOpERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 117
 15  mongod                              0x000000010712179b _ZN5mongo8runQueryERNS_7MessageERNS_12QueryMessageERNS_5CurOpES1_ + 1595
 16  mongod                              0x0000000106fe66f2 _ZN5mongoL13receivedQueryERNS_6ClientERNS_10DbResponseERNS_7MessageE + 418
 17  mongod                              0x0000000106feb5f0 _ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE + 1136
 18  mongod                              0x00000001069006e7 _ZN5mongo16MyMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE + 261
 19  mongod                              0x0000000106d44563 _ZN5mongo3pms9threadRunEPNS_13MessagingPortE + 2275