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Commit 3f2367ba authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt
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ftrace: Cleanup regex_lock and ftrace_lock around hash updating 

Cleanup regex_lock and ftrace_lock locking points around
ftrace_ops hash update code.

The new rule is that regex_lock protects ops->*_hash
read-update-write code for each ftrace_ops. Usually,
hash update is done by following sequence.

1. allocate a new local hash and copy the original hash.
2. update the local hash.
3. move(actually, copy) back the local hash to ftrace_ops.
4. update ftrace entries if needed.
5. release the local hash.

This makes regex_lock protect #1-#4, and ftrace_lock
to protect #3, #4 and adding and removing ftrace_ops from the
ftrace_ops_list. The ftrace_lock protects #3 as well because
the move functions update the entries too.

Link: http://lkml.kernel.org/r/20130509054421.30398.83411.stgit@mhiramat-M0-7522



Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f04f24fb

kernel/trace/ftrace.c

+32 −27
Original line number Diff line number Diff line
@@ -2656,28 +2656,26 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, 
		return -ENOMEM;

	}



	iter->ops = ops;

	iter->flags = flag;



	mutex_lock(&ops->regex_lock);



	if (flag & FTRACE_ITER_NOTRACE)

		hash = ops->notrace_hash;

	else

		hash = ops->filter_hash;



	iter->ops = ops;

	iter->flags = flag;



	if (file->f_mode & FMODE_WRITE) {

		mutex_lock(&ftrace_lock);

		iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);

		mutex_unlock(&ftrace_lock);



		if (!iter->hash) {

			trace_parser_put(&iter->parser);

			kfree(iter);

			return -ENOMEM;

			ret = -ENOMEM;

			goto out_unlock;

		}

	}



	mutex_lock(&ops->regex_lock);



	if ((file->f_mode & FMODE_WRITE) &&

	    (file->f_flags & O_TRUNC))

		ftrace_filter_reset(iter->hash);
@@ -2697,6 +2695,8 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, 
		}

	} else

		file->private_data = iter;



 out_unlock:

	mutex_unlock(&ops->regex_lock);



	return ret;
@@ -3012,7 +3012,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops, 
	if (WARN_ON(not))

		return -EINVAL;



	mutex_lock(&ftrace_lock);

	mutex_lock(&trace_probe_ops.regex_lock);



	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);

	if (!hash) {
@@ -3070,14 +3070,16 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops, 


	} while_for_each_ftrace_rec();



	mutex_lock(&ftrace_lock);

	ret = ftrace_hash_move(&trace_probe_ops, 1, orig_hash, hash);

	if (ret < 0)

		count = ret;



	__enable_ftrace_function_probe();

	mutex_unlock(&ftrace_lock);



 out_unlock:

	mutex_unlock(&ftrace_lock);

	mutex_unlock(&trace_probe_ops.regex_lock);

	free_ftrace_hash(hash);



	return count;
@@ -3117,7 +3119,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops, 
			return;

	}



	mutex_lock(&ftrace_lock);

	mutex_lock(&trace_probe_ops.regex_lock);



	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);

	if (!hash)
@@ -3155,6 +3157,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops, 
			list_add(&entry->free_list, &free_list);

		}

	}

	mutex_lock(&ftrace_lock);

	__disable_ftrace_function_probe();

	/*

	 * Remove after the disable is called. Otherwise, if the last
@@ -3166,9 +3169,10 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops, 
		list_del(&entry->free_list);

		ftrace_free_entry(entry);

	}

	mutex_unlock(&ftrace_lock);

		

 out_unlock:

	mutex_unlock(&ftrace_lock);

	mutex_unlock(&trace_probe_ops.regex_lock);

	free_ftrace_hash(hash);

}
@@ -3284,11 +3288,10 @@ ftrace_regex_write(struct file *file, const char __user *ubuf, 
	} else

		iter = file->private_data;



	mutex_lock(&iter->ops->regex_lock);



	ret = -ENODEV;

	if (unlikely(ftrace_disabled))

		goto out_unlock;

		return -ENODEV;



	/* iter->hash is a local copy, so we don't need regex_lock */



	parser = &iter->parser;

	read = trace_get_user(parser, ubuf, cnt, ppos);
@@ -3299,13 +3302,11 @@ ftrace_regex_write(struct file *file, const char __user *ubuf, 
					   parser->idx, enable);

		trace_parser_clear(parser);

		if (ret < 0)

			goto out_unlock;

			goto out;

	}



	ret = read;

out_unlock:

	mutex_unlock(&iter->ops->regex_lock);



 out:

	return ret;

}
@@ -3357,16 +3358,19 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len, 
	if (unlikely(ftrace_disabled))

		return -ENODEV;



	mutex_lock(&ops->regex_lock);



	if (enable)

		orig_hash = &ops->filter_hash;

	else

		orig_hash = &ops->notrace_hash;



	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);

	if (!hash)

		return -ENOMEM;

	if (!hash) {

		ret = -ENOMEM;

		goto out_regex_unlock;

	}



	mutex_lock(&ops->regex_lock);

	if (reset)

		ftrace_filter_reset(hash);

	if (buf && !ftrace_match_records(hash, buf, len)) {
@@ -3584,8 +3588,6 @@ int ftrace_regex_release(struct inode *inode, struct file *file) 
	} else

		iter = file->private_data;



	mutex_lock(&iter->ops->regex_lock);



	parser = &iter->parser;

	if (trace_parser_loaded(parser)) {

		parser->buffer[parser->idx] = 0;
@@ -3594,6 +3596,8 @@ int ftrace_regex_release(struct inode *inode, struct file *file) 


	trace_parser_put(parser);



	mutex_lock(&iter->ops->regex_lock);



	if (file->f_mode & FMODE_WRITE) {

		filter_hash = !!(iter->flags & FTRACE_ITER_FILTER);
@@ -3611,10 +3615,11 @@ int ftrace_regex_release(struct inode *inode, struct file *file) 


		mutex_unlock(&ftrace_lock);

	}



	mutex_unlock(&iter->ops->regex_lock);

	free_ftrace_hash(iter->hash);

	kfree(iter);



	mutex_unlock(&iter->ops->regex_lock);

	return 0;

}