linux-kernel - Re: [PATCH v3 0/8] cleanup: Introduce ACQUIRE(), a guard() for conditional locks

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Message-ID: <aIo18KZpmKuR4hVZ@black.igk.intel.com>
Date: Wed, 30 Jul 2025 17:10:40 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Dan Williams <dan.j.williams@...el.com>,
	Nathan Chancellor <nathan@...nel.org>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alison Schofield <alison.schofield@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	David Lechner <dlechner@...libre.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Ira Weiny <ira.weiny@...el.com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Shiju Jose <shiju.jose@...wei.com>,
	Vishal Verma <vishal.l.verma@...el.com>
Subject: Re: [PATCH v3 0/8] cleanup: Introduce ACQUIRE(), a guard() for
 conditional locks

On Fri, Jul 11, 2025 at 04:49:24PM -0700, Dan Williams wrote:
> Changes since v2 [1]:
> - Pick up Acks and Reviews
> - Whitespace fixups for cleanup.h changes (Jonathan)
> - Use consistent local variable style for ACQUIRE_ERR() (Jonathan)
>   - Not addressed: switch to less compact style ACQUIRE_ERR()
> - Not addressed: pickup checkpatch change for ACQUIRE_ERR() style in
>   this series (Alison)
> - Drop the cxl_decoder_detach() CLASS() and convert to a helper function (Jonathan)
> - Refactor attach_target() to make it easier to read (Jonathan)
> 
> [1]: http://lore.kernel.org/20250619050416.782871-1-dan.j.williams@intel.com
> 
> For those new to this set, the motivation for this work is that the CXL
> subsystem adopted scope-based-cleanup helpers and achieved some decent
> cleanups. However, that work stalled with conditional locks. It stalled
> due to the pain points of scoped_cond_guard(). See patch1.
> 
> In the interim, approaches like rwsem_read_intr_acquire() attempted to
> workaround the pain points, but started a "parallel universe" of helpers
> that is not sustainable.
> 
>     0c6e6f1357cb cxl/edac: Add CXL memory device patrol scrub control feature
> 
> Peter fixed all of this up in a manner consistent with existing guards.
> Take that proposal and run with it to unblock further cleanups of "goto"
> in unwind paths in the CXL subsystem.
> 
> Potential follow-on work identified by this effort:
> 
> - __GUARD_IS_ERR() asm helper [2]
> - Checkpatch fixups for proposed ACQUIRE_ERR() style [3]
> 
> [2]: http://lore.kernel.org/20250514064624.GA24938@noisy.programming.kicks-ass.net
> [3]: http://lore.kernel.org/aGXDMZB6omShJpoj@aschofie-mobl2.lan

This series broke `make W=1` build vor clang. +Cc Nathan.

Par exemple:

/kernel/time/posix-timers.c:89:1: error: unused function 'class_lock_timer_lock_err' [-Werror,-Wunused-function]
   89 | DEFINE_CLASS_IS_COND_GUARD(lock_timer);
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/include/linux/cleanup.h:376:2: note: expanded from macro 'DEFINE_CLASS_IS_COND_GUARD'
  376 |         __DEFINE_GUARD_LOCK_PTR(_name, _T)
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/include/linux/cleanup.h:358:20: note: expanded from macro '__DEFINE_GUARD_LOCK_PTR'
  358 |         static inline int class_##_name##_lock_err(class_##_name##_t *_T)   \
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~
<scratch space>:24:1: note: expanded from here
   24 | class_lock_timer_lock_err
      | ^~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

-- 
With Best Regards,
Andy Shevchenko