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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6fd74e3266bsm553516d6.53.2025.06.25.08.05.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Jun 2025 08:05:50 -0700 (PDT) Received: from phl-compute-08.internal (phl-compute-08.phl.internal [10.202.2.48]) by mailfauth.phl.internal (Postfix) with ESMTP id 76F22F40066; Wed, 25 Jun 2025 11:05:49 -0400 (EDT) Received: from phl-mailfrontend-01 ([10.202.2.162]) by phl-compute-08.internal (MEProxy); Wed, 25 Jun 2025 11:05:49 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtddvgddvfedtlecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpuffrtefokffrpgfnqfghnecuuegr ihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjug hrpeffhffvvefukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpeeuohhquhhnucfh vghnghcuoegsohhquhhnrdhfvghnghesghhmrghilhdrtghomheqnecuggftrfgrthhtvg hrnheptddtudegueevgefhgfeuffetffeuheekgedtffefhefhjeffhffgfeeggeetgefh necuffhomhgrihhnpegvfhhfihgtihhoshdrtghomhenucevlhhushhtvghrufhiiigvpe dtnecurfgrrhgrmhepmhgrihhlfhhrohhmpegsohhquhhnodhmvghsmhhtphgruhhthhhp vghrshhonhgrlhhithihqdeiledvgeehtdeigedqudejjeekheehhedvqdgsohhquhhnrd hfvghngheppehgmhgrihhlrdgtohhmsehfihigmhgvrdhnrghmvgdpnhgspghrtghpthht ohepvdeipdhmohguvgepshhmthhpohhuthdprhgtphhtthhopehmrghthhhivghurdguvg hsnhhohigvrhhssegvfhhfihgtihhoshdrtghomhdprhgtphhtthhopehlihhnuhigqdhk vghrnhgvlhesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtthhopehrtghusehvgh gvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhkmhhmsehlihhsthhsrdhlihhn uhigrdguvghvpdhrtghpthhtohepphgvthgvrhiisehinhhfrhgruggvrggurdhorhhgpd hrtghpthhtohepmhhinhhgoheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepfihilhhl sehkvghrnhgvlhdrohhrghdprhgtphhtthhopehlohhnghhmrghnsehrvgguhhgrthdrtg homhdprhgtphhtthhopegurghvvgesshhtghholhgrsghsrdhnvght X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 25 Jun 2025 11:05:48 -0400 (EDT) Date: Wed, 25 Jun 2025 08:05:48 -0700 From: Boqun Feng To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, lkmm@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Davidlohr Bueso , "Paul E. McKenney" , Josh Triplett , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Breno Leitao , aeh@meta.com, netdev@vger.kernel.org, edumazet@google.com, jhs@mojatatu.com, kernel-team@meta.com, Erik Lundgren Subject: Re: [PATCH 1/8] Introduce simple hazard pointers Message-ID: References: <20250625031101.12555-1-boqun.feng@gmail.com> <20250625031101.12555-2-boqun.feng@gmail.com> <3e2a80e6-b3c5-44dd-b290-1d140cc427ff@efficios.com> Precedence: bulk X-Mailing-List: lkmm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e2a80e6-b3c5-44dd-b290-1d140cc427ff@efficios.com> On Wed, Jun 25, 2025 at 10:25:23AM -0400, Mathieu Desnoyers wrote: > On 2025-06-24 23:10, Boqun Feng wrote: > [...] > > + > > +static inline void shazptr_clear(struct shazptr_guard guard) > > +{ > > + /* Only clear the slot when the outermost guard is released */ > > + if (likely(!guard.use_wildcard)) > > + smp_store_release(guard.slot, NULL); /* Pair with ACQUIRE at synchronize_shazptr() */ > > How is the wildcard ever cleared ? > The outermost shazptr_guard will have .use_wildcard being false, so it will clear the wildcard. E.g. g1 = shazptr_acqure(a); // g1->use_wildcard is false // this cpu's hazptr slot is 'a'. g2 = shazptr_acqure(b); // g2->use_wildcard is true // this cpu's hazptr slot becomes // WILDCARD. shazptr_clear(g2); // do nothing shazptr_clear(g1); // clear this cpu's hazptr slot to NULL. Regards, Boqun > Thanks, > > Mathieu > > > -- > Mathieu Desnoyers > EfficiOS Inc. > https://www.efficios.com