kernel/rcu/tree_stall.h

86  * Note that sampling of the .gp_start and .gp_seq fields must be done
102 	smp_mb(); // .gp_seq before second .gp_start
104 	return !time_before(j, READ_ONCE(rcu_state.gp_start) + d);
176 	WRITE_ONCE(rcu_state.gp_start, j);
178 	smp_mb(); // ->gp_start before ->jiffies_stall and caller's ->gp_seq.
754 	 * rcu_state.jiffies_stall, then rcu_state.gp_start, and finally
758 	 * can occur if we get an new value of rcu_state.gp_start and a old
766 	 * and rcu_state.gp_start suffice to forestall false positives.
772 	gps = READ_ONCE(rcu_state.gp_start);
773 	smp_rmb(); /* ...and finally ->gp_start before ->gp_seq again. */
893 	js = j - data_race(READ_ONCE(rcu_state.gp_start));
895 	pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
1015 			__func__, jiffies - data_race(READ_ONCE(rcu_state.gp_start)));