Re: [PATCH 06/10] Input: sparcspkr - use cleanup facility for device_node

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Oct 11, 2024 at 12:09:01AM +0200, Javier Carrasco wrote:

> I think that the issue you are talking about is that the goto will
> trigger the cleanup function of the device_node, which will not be
> initialized at that point.

... and gcc will compile that without an error.  Clang will not, but
you need to watch out for build coverage in arch-specific code -
clang doesn't cover every architecture (and won't cover some of them,
no matter what - alpha, for example).

As for the scope changes... note that you've delayed the moment of
of_node_put() in some of those.  It's harmless for device_node, but
try something of that sort with e.g.

	mutex_lock(&lock);
	something();
	mutex_unlock(&lock);
	foo();
	return 0;

where foo() itself grabs the same lock and it's not harmless at all -

	guard(mutex)(&lock);
	something();
	foo();
	return 0;

is equivalent to moving mutex_unlock() to the end of scope, i.e. past
the call of foo(), resulting in

	mutex_lock(&lock);
	something();
	foo();			// deadlock
	mutex_unlock(&lock);
	return 0;

__cleanup *is* a useful tool, when used carefully, but you really
have to watch out for crap of that sort.