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Commit 07fd5515 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

ftrace: Free hash with call_rcu_sched() 



When a hash is modified and might be in use, we need to perform
a schedule RCU operation on it, as the hashes will soon be used
directly in the function tracer callback.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 2b499381

kernel/trace/ftrace.c

+28 −27
Original line number Original line Diff line number Diff line
@@ -913,6 +913,7 @@ struct ftrace_hash { 
	unsigned long		size_bits;

	unsigned long		size_bits;

	struct hlist_head	*buckets;

	struct hlist_head	*buckets;

	unsigned long		count;

	unsigned long		count;

	struct rcu_head		rcu;

};

};





/*

/*
@@ -1058,6 +1059,21 @@ static void free_ftrace_hash(struct ftrace_hash *hash) 
	kfree(hash);

	kfree(hash);

}

}





static void __free_ftrace_hash_rcu(struct rcu_head *rcu)

{

	struct ftrace_hash *hash;



	hash = container_of(rcu, struct ftrace_hash, rcu);

	free_ftrace_hash(hash);

}



static void free_ftrace_hash_rcu(struct ftrace_hash *hash)

{

	if (!hash || hash == EMPTY_HASH)

		return;

	call_rcu_sched(&hash->rcu, __free_ftrace_hash_rcu);

}



static struct ftrace_hash *alloc_ftrace_hash(int size_bits)

static struct ftrace_hash *alloc_ftrace_hash(int size_bits)

{

{

	struct ftrace_hash *hash;

	struct ftrace_hash *hash;
@@ -1122,7 +1138,8 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	struct ftrace_func_entry *entry;

	struct ftrace_func_entry *entry;

	struct hlist_node *tp, *tn;

	struct hlist_node *tp, *tn;

	struct hlist_head *hhd;

	struct hlist_head *hhd;

	struct ftrace_hash *hash = *dst;

	struct ftrace_hash *old_hash;

	struct ftrace_hash *new_hash;

	unsigned long key;

	unsigned long key;

	int size = src->count;

	int size = src->count;

	int bits = 0;

	int bits = 0;
@@ -1133,13 +1150,11 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	 * the empty_hash.

	 * the empty_hash.

	 */

	 */

	if (!src->count) {

	if (!src->count) {

		free_ftrace_hash(*dst);

		free_ftrace_hash_rcu(*dst);

		*dst = EMPTY_HASH;

		rcu_assign_pointer(*dst, EMPTY_HASH);

		return 0;

		return 0;

	}

	}





	ftrace_hash_clear(hash);



	/*

	/*

	 * Make the hash size about 1/2 the # found

	 * Make the hash size about 1/2 the # found

	 */

	 */
@@ -1150,28 +1165,10 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	if (bits > FTRACE_HASH_MAX_BITS)

	if (bits > FTRACE_HASH_MAX_BITS)

		bits = FTRACE_HASH_MAX_BITS;

		bits = FTRACE_HASH_MAX_BITS;





	/* We can't modify the empty_hash */

	new_hash = alloc_ftrace_hash(bits);

	if (hash == EMPTY_HASH) {

	if (!new_hash)

		/* Create a new hash */

		*dst = alloc_ftrace_hash(bits);

		if (!*dst) {

			*dst = EMPTY_HASH;

			return -ENOMEM;

		}

		hash = *dst;

	} else {

		size = 1 << bits;



		/* Use the old hash, but create new buckets */

		hhd = kzalloc(sizeof(*hhd) * size, GFP_KERNEL);

		if (!hhd)

		return -ENOMEM;

		return -ENOMEM;





		kfree(hash->buckets);

		hash->buckets = hhd;

		hash->size_bits = bits;

	}



	size = 1 << src->size_bits;

	size = 1 << src->size_bits;

	for (i = 0; i < size; i++) {

	for (i = 0; i < size; i++) {

		hhd = &src->buckets[i];

		hhd = &src->buckets[i];
@@ -1181,10 +1178,14 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
			else

			else

				key = 0;

				key = 0;

			remove_hash_entry(src, entry);

			remove_hash_entry(src, entry);

			__add_hash_entry(hash, entry);

			__add_hash_entry(new_hash, entry);

		}

		}

	}

	}





	old_hash = *dst;

	rcu_assign_pointer(*dst, new_hash);

	free_ftrace_hash_rcu(old_hash);



	return 0;

	return 0;

}

}