From patchwork Thu Jun 20 16:11:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13705803 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03A741B1514; Thu, 20 Jun 2024 16:11:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718899904; cv=none; b=t4gPFNxBXsML8ZwYJ2yDl/scmwCLGm2r4/kU36kDxgmiERTX3ItDpaimxgVJKjbbZN+0lOwksB5MUd39PLf54Sghu29yVJz49MdMdb5etNnC5G9MbP9i76uv98/H53pCBc+Jbh+BFnxkDasXzgIMiuyyKiiqyQ0m/EkrdkADxgA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718899904; c=relaxed/simple; bh=moqkrVqx95CFhHpEKKGXhdPr5fPQ9IbFq3m1fia5tT4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=XCq880x7/fpH3NaVzdDgQqtTLubt73f8Um60tdqVTpX6zt2vF/BW2gyhJE1Ly5OnQ3nCgPuD9gfyKcl33N2XlwFxpWgWrkbnOewpfZvzDv5gBvQWsGWTst8PdANXHZ3JqdVbaBmu5LAZy8ILYX+qZt3/j2ZoPNTyorLsmttB1nk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hVwCxk7m; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hVwCxk7m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A72BBC4AF0A; Thu, 20 Jun 2024 16:11:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718899903; bh=moqkrVqx95CFhHpEKKGXhdPr5fPQ9IbFq3m1fia5tT4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hVwCxk7mflF3ByQBM3cGd6r6Lu94QLOknEe7PvZUcLYt/uiaYTUVGaBrYhS5FiwX7 kfxUJf0r2xhcRrcncw9rKnIFWR5uJYwGU75mAfaNh03kwBUohSctZqml6YJ2IJVamJ 8iS+ifUihbHnTvvpuDxtuOnTgSMnu7I1HQXHLIMp+k0an2KolZDorsHzU6dlX+KsqS M0OJEohb1TewF4FNja9lXSQzxhXycxtESiGBAqSF+VRCB55gDBaYDQ12WUClGPr1Vt ERCF0ISiIJGjFfxtIBYXSczhNjQ657rscHBlwAjCoXXdx5zMAuC6IdV9KFc8nUhkqp w5nHDytpDwrTw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 540D9CE0D11; Thu, 20 Jun 2024 09:11:43 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Kent Overstreet Subject: [PATCH rcu 3/3] srcu: Fill out polled grace-period APIs Date: Thu, 20 Jun 2024 09:11:42 -0700 Message-Id: <20240620161142.2057652-3-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <8ec14282-a768-49eb-b870-c2ee51e91f8b@paulmck-laptop> References: <8ec14282-a768-49eb-b870-c2ee51e91f8b@paulmck-laptop> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit adds the get_completed_synchronize_srcu() and the same_state_synchronize_srcu() functions. The first returns a cookie that is always interpreted as corresponding to an expired grace period. The second does an equality comparison of a pair of cookies. Signed-off-by: Paul E. McKenney Cc: Kent Overstreet --- include/linux/srcu.h | 31 +++++++++++++++++++++++++++++++ kernel/rcu/srcutiny.c | 3 ++- kernel/rcu/srcutree.c | 3 ++- 3 files changed, 35 insertions(+), 2 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f664cba7a80c2..6f6cb5fc12424 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -57,6 +57,20 @@ void cleanup_srcu_struct(struct srcu_struct *ssp); int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); void synchronize_srcu(struct srcu_struct *ssp); + +#define SRCU_GET_STATE_COMPLETED 0x1 + +/** + * get_completed_synchronize_srcu - Return a pre-completed polled state cookie + * + * Returns a value that poll_state_synchronize_srcu() will always treat + * as a cookie whose grace period has already completed. + */ +static inline unsigned long get_completed_synchronize_srcu(void) +{ + return SRCU_GET_STATE_COMPLETED; +} + unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); @@ -65,6 +79,23 @@ bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); // not-yet-completed SRCU grace periods. #define NUM_ACTIVE_SRCU_POLL_OLDSTATE 2 +/** + * same_state_synchronize_srcu - Are two old-state values identical? + * @oldstate1: First old-state value. + * @oldstate2: Second old-state value. + * + * The two old-state values must have been obtained from either + * get_state_synchronize_srcu(), start_poll_synchronize_srcu(), or + * get_completed_synchronize_srcu(). Returns @true if the two values are + * identical and @false otherwise. This allows structures whose lifetimes + * are tracked by old-state values to push these values to a list header, + * allowing those structures to be slightly smaller. + */ +static inline bool same_state_synchronize_srcu(unsigned long oldstate1, unsigned long oldstate2) +{ + return oldstate1 == oldstate2; +} + #ifdef CONFIG_NEED_SRCU_NMI_SAFE int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 5afd5cf494dba..549c03336ee97 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -277,7 +277,8 @@ bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie) unsigned long cur_s = READ_ONCE(ssp->srcu_idx); barrier(); - return ULONG_CMP_GE(cur_s, cookie) || ULONG_CMP_LT(cur_s, cookie - 3); + return cookie == SRCU_GET_STATE_COMPLETED || + ULONG_CMP_GE(cur_s, cookie) || ULONG_CMP_LT(cur_s, cookie - 3); } EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 15dc22a8ff5ab..d6a4047719cb0 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1543,7 +1543,8 @@ EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu); */ bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie) { - if (!rcu_seq_done(&ssp->srcu_sup->srcu_gp_seq, cookie)) + if (cookie != SRCU_GET_STATE_COMPLETED && + !rcu_seq_done(&ssp->srcu_sup->srcu_gp_seq, cookie)) return false; // Ensure that the end of the SRCU grace period happens before // any subsequent code that the caller might execute.