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Date: Mon, 12 May 2025 20:25:59 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: dan.j.williams@intel.com
Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
	David Lechner <dlechner@baylibre.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
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	Alison Schofield <alison.schofield@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Ira Weiny <ira.weiny@intel.com>
Subject: Re: [PATCH 1/7] cleanup: Introduce DEFINE_ACQUIRE() a CLASS() for
 conditional locking
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In-Reply-To: <20250512105026.GP4439@noisy.programming.kicks-ass.net>

On Mon, May 12, 2025 at 12:50:26PM +0200, Peter Zijlstra wrote:

> +#define __GUARD_ERR(_ptr) \
> +	({ long _rc = (__force unsigned long)(_ptr); \
> +	   if (!_rc) { _rc = -EBUSY; } if (!IS_ERR_VALUE(_rc)) { _rc = 0; } \
> +	   _rc; })
> +

>  #define DEFINE_GUARD(_name, _type, _lock, _unlock) \
> -	DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \
> +	DEFINE_CLASS(_name, _type, if (!__GUARD_ERR(_T)) { _unlock; }, ({ _lock; _T; }), _type _T); \
>  	DEFINE_CLASS_IS_GUARD(_name)

GCC is 'stupid' and this generates atrocious code. I'll play with it.