how to run a uvm_sequence_library from a virtual sequence??

[pratyaksharn]

Hello,

Scenario

1. I have two UVCs driving the DUT. host and top

2. I am using virtual sequence to run the sequences of host and top

3. I have created a host_seq_lib of type host_sequence_library.

4. I want to randomly execute any of the sequences from the sequence library until a signal rises.

Problem :

I try to run host_seq_lib in my virtual sequence like this.

class rcc_full_flag_seq extends uvm_sequence;
 
	// provide the implementations of virtual methods like get_type()
	`uvm_object_utils(rcc_full_flag_seq)
	`uvm_declare_p_sequencer(badge_vsequencer)
 
	// top de-assert reset sequence
	top_ctrl_disable_reset_seq top_disable_reset;
	top_ctrl_enable_reset_seq top_enable_reset;
 
	host_seq_lib	host_seqs;
   host_config cfg;
 
	// new constructor
	function new(string name="rcc_full_flag_seq");
		super.new(name);
	endfunction : new	
 
   virtual task pre_body();
		// Get the configuration object
		if(!uvm_config_db #(host_config)::get(null, get_full_name(), "host", host_cfg)) begin
	    `uvm_error("HOST_CFG", "host_config not found");
		end
		host_seqs.selection_mode = UVM_SEQ_LIB_RANDC;
		host_seqs.min_random_count = 15;
		host_seqs.max_random_count = 30;
	endtask
 
	virtual task body();
			`uvm_do_on(top_disable_reset, p_sequencer.top_ctrl_seqr)
			fork
			repeat(30);
			begin		
				`uvm_do_on(host_seqs, p_sequencer.host_seqr)
			end
			host_cfg.wait_for_full_rise();
			join_any
	endtask
endclass

HOwever I get an error

* Fatal: (vsim-131) /home/prra/trunk/badgeComponent/uvm_testbench/rccgpu_tb/tb/badge_virtual_seqs.sv(53): Null instance encountered when dereferencing '/badge_tb_top/rcc_full_flag_seq::pre_body/this*.host_seqs

Question - Can I run a sequence library inside a virtual_sequence?

[IChip]

In pre_body() host_seqs is an null until it's created in body().