rcu: Add comment documenting how rcu_seq_snap works

	WRITE_ONCE(*sp, rcu_seq_endval(sp));

}

/* Take a snapshot of the update side's sequence number. */

/*

 * rcu_seq_snap - Take a snapshot of the update side's sequence number.

 *

 * This function returns the earliest value of the grace-period sequence number

 * that will indicate that a full grace period has elapsed since the current

 * time.  Once the grace-period sequence number has reached this value, it will

 * be safe to invoke all callbacks that have been registered prior to the

 * current time. This value is the current grace-period number plus two to the

 * power of the number of low-order bits reserved for state, then rounded up to

 * the next value in which the state bits are all zero.

 */

static inline unsigned long rcu_seq_snap(unsigned long *sp)

{

	unsigned long s;