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[2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id q16sm4118338pfu.36.2021.10.20.13.10.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Oct 2021 13:10:09 -0700 (PDT) Date: Wed, 20 Oct 2021 10:10:07 -1000 From: Tejun Heo To: Pavel Begunkov Cc: linux-block@vger.kernel.org, Jens Axboe , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Lameter , Dennis Zhou Subject: Re: [PATCH 1/2] percpu_ref: percpu_ref_tryget_live() version holding RCU Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 713B0400208F X-Stat-Signature: 81se4xzhqpno7dgkjdmryahueos3d9se Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=Ra0L6ar+; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=pass (imf18.hostedemail.com: domain of htejun@gmail.com designates 209.85.216.52 as permitted sender) smtp.mailfrom=htejun@gmail.com X-HE-Tag: 1634760607-458556 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002157, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 20, 2021 at 09:03:18PM +0100, Pavel Begunkov wrote: > +/** > + * percpu_ref_tryget_live_rcu - same as percpu_ref_tryget_live() but the > + * caller is responsible for taking RCU. > + * > + * This function is safe to call as long as @ref is between init and exit. > + */ > +static inline bool percpu_ref_tryget_live_rcu(struct percpu_ref *ref) > +{ > + unsigned long __percpu *percpu_count; > + bool ret = false; > + > + if (likely(__ref_is_percpu(ref, &percpu_count))) { > + this_cpu_inc(*percpu_count); > + ret = true; > + } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) { > + ret = atomic_long_inc_not_zero(&ref->data->count); > + } > + return ret; > +} Can we please add rcu_read_lock_held() assertion? Other than that, looks fine to me. Thanks. -- tejun