bpf: Update locking comment in hashtab code

	.map_delete_batch =			\

	generic_map_delete_batch

/*

 * The bucket lock has two protection scopes:

 *

 * 1) Serializing concurrent operations from BPF programs on differrent

 *    CPUs

 *

 * 2) Serializing concurrent operations from BPF programs and sys_bpf()

 *

 * BPF programs can execute in any context including perf, kprobes and

 * tracing. As there are almost no limits where perf, kprobes and tracing

 * can be invoked from the lock operations need to be protected against

 * deadlocks. Deadlocks can be caused by recursion and by an invocation in

 * the lock held section when functions which acquire this lock are invoked

 * from sys_bpf(). BPF recursion is prevented by incrementing the per CPU

 * variable bpf_prog_active, which prevents BPF programs attached to perf

 * events, kprobes and tracing to be invoked before the prior invocation

 * from one of these contexts completed. sys_bpf() uses the same mechanism

 * by pinning the task to the current CPU and incrementing the recursion

 * protection accross the map operation.

 */

struct bucket {

	struct hlist_nulls_head head;

	raw_spinlock_t lock;

		 */

	}

	/* bpf_map_update_elem() can be called in_irq() */

	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);

		return -ENOMEM;

	memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);

	/* bpf_map_update_elem() can be called in_irq() */

	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);

	b = __select_bucket(htab, hash);

	head = &b->head;

	/* bpf_map_update_elem() can be called in_irq() */

	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);

			return -ENOMEM;

	}

	/* bpf_map_update_elem() can be called in_irq() */

	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);