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([216.195.201.23]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36ca38d46fcsm9019567eec.13.2026.11.04.08.55.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 08:55:47 -0800 (PST) From: Kunwu Chan To: paulmck@kernel.org, boqun@kernel.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, corbet@lwn.net, mingo@redhat.com, frederic@kernel.org, neeraj.upadhyay@kernel.org, josh@joshtriplett.org, urezki@gmail.com, dave@stgolabs.net Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com, will@kernel.org, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com, dlustig@nvidia.com, joelagnelf@nvidia.com, skhan@linuxfoundation.org, rdunlap@infradead.org, longman@redhat.com, rostedt@goodmis.org, qiang.zhang@linux.dev, kunwu.chan@gmail.com, brads@mainlining.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, lkmm@lists.linux.dev, linux-doc@vger.kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH 03/28] hazptr: Add scoped_guard() support Date: Thu, 5 Nov 2026 00:54:21 +0800 Message-ID: <20261104165504.2430480-4-kunwu.chan@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261104165504.2430480-1-kunwu.chan@gmail.com> References: <20261104165504.2430480-1-kunwu.chan@gmail.com> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a scoped_guard() class for hazptr so that callers can pair hazptr_acquire() with hazptr_release() on scope exit. The guard holds a pointer to a caller-provided hazptr_ctx rather than embedding it. The ctx must remain at a stable address while the hazard pointer is held because the slow path can chain its backup slot into the overflow list by address. Suggested-by: Boqun Feng Signed-off-by: Kunwu Chan Acked-by: Bradley Morgan --- include/linux/hazptr.h | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/include/linux/hazptr.h b/include/linux/hazptr.h index d37792af3493..3372b1cdbee6 100644 --- a/include/linux/hazptr.h +++ b/include/linux/hazptr.h @@ -341,6 +341,43 @@ void hazptr_release(struct hazptr_ctx *ctx, void *addr) hazptr_unchain_backup_slot(ctx); } + +/** + * struct hazptr_guard - cleanup.h guard for a single hazard pointer + * + * @ctx: Pointer to the caller-provided hazard-pointer context. + * @addr: The address returned by the matching hazptr_acquire(). + */ +struct hazptr_guard { + struct hazptr_ctx *ctx; + void *addr; +}; + +/** + * hazptr_guard_acquire - Acquire a hazard pointer for scoped_guard() use + * + * @ctx: The caller-provided hazard-pointer context. + * @addr_p: Pointer to the pointer that is to be hazard-pointer protected. + * + * Acquire a hazard pointer using @ctx and return a guard that + * cleanup.h releases via hazptr_release() on scope exit. + */ +static inline struct hazptr_guard +hazptr_guard_acquire(struct hazptr_ctx *ctx, void * const *addr_p) +{ + struct hazptr_guard g; + + g.ctx = ctx; + g.addr = hazptr_acquire(ctx, addr_p); + return g; +} + +DEFINE_CLASS(hazptr, struct hazptr_guard, + hazptr_release(_T.ctx, _T.addr), + hazptr_guard_acquire(ctx, addr_p), + struct hazptr_ctx *ctx, void * const *addr_p) +DEFINE_CLASS_IS_UNCONDITIONAL(hazptr) + void hazptr_init(void); #endif /* _LINUX_HAZPTR_H */ -- 2.43.0