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Why we get SEQREQZMB when jumping to another phase

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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.

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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:



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