stall in parallel_for

Hello,

I am using TBB 4.1 update 3 (Linux) on a workstation with 4 Intel Xeon sockets (X7560, total 32 cores, 64 threads, using Intel compiler 12.0.4) and testing with 4 MPI processes---each configured to use 8 threads (task_scheduler_init init(8)). Each processes has three task groups and each task group invokes parallel_for in multiple levels.

If I use the debug version of TBB libraries, I am seeing the following assertion failures (mostly the first one, and somewhat less frequently the second one)