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s=arc-20220608; d=hostedemail.com; t=1736577131; a=rsa-sha256; cv=none; b=AjJS0VFNSa4akxpYmaX+W7RhAQWNTDatVkfahcQzyD/dQ3ojlwGdMZztkJ6kkPp2xzYxc+ cR6ObeYrU6d+56+yLzg29Ht5exxZJAneC5e/TB2xkQnUx45rdsk3+C+7qHzslcHTank+NJ Lm/mGVFZIVN3MDgzcRY1cj8iPrO+umM= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf27.hostedemail.com: domain of hdanton@sina.com designates 218.30.115.63 as permitted sender) smtp.mailfrom=hdanton@sina.com X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([113.118.71.135]) by sina.com (10.185.250.22) with ESMTP id 67821062000050DC; Sat, 11 Jan 2025 14:32:04 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 9460547602767 X-SMAIL-UIID: DB3CA4E98B2C490FAED46474773FD411-20250111-143204-1 From: Hillf Danton To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v9 10/17] refcount: introduce __refcount_{add|inc}_not_zero_limited Date: Sat, 11 Jan 2025 14:31:49 +0800 Message-ID: <20250111063152.1638-1-hdanton@sina.com> In-Reply-To: <20250111042604.3230628-11-surenb@google.com> References: <20250111042604.3230628-1-surenb@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: q4o4i8qdh4zbsaxj3nhi9o51cgkwwbo9 X-Rspamd-Queue-Id: 3E36540006 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1736577129-345199 X-HE-Meta: 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 wUuL9Zml VHkqE+OSR4VGYBU0HSkNLNkTqD1XMP3gbjv6zUGnT1zYtE4w5w6/Dt50u5a1KuGPFFzUIsx0BXJYgLPF6fGjjbA1dPL9X2SaLPcW82g0yaaHLcW45qV63iq3XDOCuIiQe8v9R/AEg8rpAZrJOs+unGhMgo3ppq0Iu+yy+Q2APO2ilbgKtBqirn6+hZw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.041970, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 10 Jan 2025 20:25:57 -0800 Suren Baghdasaryan > -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?