linux-kernel - Re: [PATCH v9 10/17] refcount: introduce __refcount_{add|inc}_not_zero

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Message-ID: <20250111063152.1638-1-hdanton@sina.com>
Date: Sat, 11 Jan 2025 14:31:49 +0800
From: Hillf Danton <hdanton@...a.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: akpm@...ux-foundation.org,
	peterz@...radead.org,
	willy@...radead.org,
	hannes@...xchg.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	kernel-team@...roid.com
Subject: Re: [PATCH v9 10/17] refcount: introduce __refcount_{add|inc}_not_zero_limited

On Fri, 10 Jan 2025 20:25:57 -0800 Suren Baghdasaryan <surenb@...gle.com>
> -bool __refcount_add_not_zero(int i, refcount_t *r, int *oldp)
> +bool __refcount_add_not_zero_limited(int i, refcount_t *r, int *oldp,
> +				     int limit)
>  {
>  	int old = refcount_read(r);
>  
>  	do {
>  		if (!old)
>  			break;
> +
> +		if (statically_true(limit == INT_MAX))
> +			continue;
> +
> +		if (i > limit - old) {
> +			if (oldp)
> +				*oldp = old;
> +			return false;
> +		}
>  	} while (!atomic_try_cmpxchg_relaxed(&r->refs, &old, old + i));

The acquire version should be used, see atomic_long_try_cmpxchg_acquire()
in kernel/locking/rwsem.c.

Why not use the atomic_long_t without bothering to add this limited version?