Why we get SEQREQZMB when jumping to another phase

[zhiharev]

I have a reset sequence, which starts as default_sequence for reset_phase. For main_phase I have some sequence, which is started as default sequence.

At some time I jump from main_phase to reset_phase. Then I get error:

 

[sEQREQZMB] The task responsible for requesting a wait_for_grant on sequencer 'uvm_test_top.env.ctb_agent.sequencer' for sequence 'default_parent_seq' has been killed, to avoid a deadlock the sequence will be removed from the arbitration queues

 

This error occures only if at the moment of the jump has_do_avaliable() of  ctb_agent.sequencer returns 1'b1. Why does it happen? I believe that jumping to another phase doesn't kill sequences.

[bhunter1972]

UVM requires that the sequencer first stop its sequences and then the driver must be certain to not call item_done on any outstanding sequences. To get this working correctly, there's a simple recipe in this paper from a few years ago, and also in the book:

 

http://sunburst-design.com/papers/HunterSNUGSV_UVM_Resets_paper.pdf

[zhiharev]

I don't think that the problem is about item_done() after stop_sequences(). When this happens we get another message.