linux-kernel - Re: [PATCH v4 06/35] cleanup: Basic compatibility with context analysis

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Message-ID: <20251216134119.GU3707837@noisy.programming.kicks-ass.net>
Date: Tue, 16 Dec 2025 14:41:19 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Marco Elver <elver@...gle.com>
Cc: Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>,
	Will Deacon <will@...nel.org>,
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Subject: Re: [PATCH v4 06/35] cleanup: Basic compatibility with context
 analysis

On Tue, Dec 16, 2025 at 02:23:19PM +0100, Marco Elver wrote:

> > Also, why do we need this second variable with cleanup; can't the
> > existing __scoped_seqlock_cleanup() get the __releases_shared()
> > attribute?
> 
> The existing __scoped_seqlock_cleanup() receives &_s (struct ss_tmp *),
> and we can't refer to the _seqlock from __scoped_seqlock_cleanup(). Even
> if I create a member seqlock_t* ss_tmp::seqlock and initialize it with
> _seqlock, the compiler can't track that the member would be an alias of
> _seqlock. The function __scoped_seqlock_next() does receive _seqlock to
> effectively release it executes for every loop, so there'd be a "lock
> imbalance" in the compiler's eyes.
> 
> So having the direct alias (even if we cast it to make it work in the
> single-statement multi-definition, the compiler doesn't care) is
> required for it to work.

Right -- it just clicked while I was walking outside. Without actual
inlining it cannot see through the constructor and track the variable :/

OK, let me stare at this more.