linux-kernel - Conditional guards

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Date: Mon, 6 May 2024 20:38:15 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Peter Zijlstra <peterz@...radead.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Conditional guards

Hi Peter

Probably a stupid question.... but I'd rather ask the expert directly :)

I am trying to fix some of the cocci warnings with guard() and there
is a  use case that I do not know how to do. I have something like:

void use_hardware(priv) {
  if (priv->model == 42)
      mutex_lock(&priv->lock):

  // DO things here

  if (priv->model ==  42)
      mutex_unlock(&priv->lock):
}

if I replace:
  if (priv->model == 42)
      mutex_lock(&priv->lock):
with
if (priv->model == 42)
     guard(mutex)(&priv->lock)

gcc screams at me:
drivers/media/dvb-core/dvb_frontend.c: In function ‘dvb_frontend_open’:
/include/linux/cleanup.h:119:9: error: expected expression before
‘class_mutex_t’
  119 |         class_##_name##_t var
__cleanup(class_##_name##_destructor) =   \
      |         ^~~~~~
/include/linux/cleanup.h:164:9: note: in expansion of macro ‘CLASS’
  164 |         CLASS(_name, __UNIQUE_ID(guard))
      |         ^~~~~
drivers/media/dvb-core/dvb_frontend.c:2776:17: note: in expansion of
macro ‘guard’
 2776 |                 guard(mutex)(&apadter->mfe_lock);


Is there a way to support something like this?

Regards!

-- 
Ricardo Ribalda