From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-244107.protonmail.ch (mail-244107.protonmail.ch [109.224.244.107]) (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 DD53C320A00; Fri, 29 May 2026 13:40:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=109.224.244.107 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780062021; cv=none; b=PjSaxa78yEvNq4ofiXP8divcgPmRmph3EGmgK86U7mXjC73MXgMbmQY44yT3WEEu8oOr5rmQDOVDSCI/6osZk49WaYgk1wjDCHHC93FXb0tBEdFW/9ovws+5hRNda5TTXdaLa4h0Sa0wublxZr2AcrB0E5vxJGtWHtJgDw0pQnQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780062021; c=relaxed/simple; bh=AqTNnLPq2ilHYXq41hOFJaefF2Ku6iuUxVu/iVxfiIQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=kh7WzHK5X/gkNj9rhrk9LPclZDoQlYdzuVkWMn239cc6y60UCqMRD/1H64YjNzPo90pfl9U4gDZzZ65VSVoAONpHKJJhPktqP+KQ81dxIq7s++9Rr6Z8rQeGgaL8ofdreOD4d8zt1/3TDFu8XG0qYdwgcSCmLE7CYTA5mc4Hy/E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=onurozkan.dev; spf=pass smtp.mailfrom=onurozkan.dev; dkim=pass (2048-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b=s++3AGjs; arc=none smtp.client-ip=109.224.244.107 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b="s++3AGjs" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=protonmail; t=1780062017; x=1780321217; bh=RS5uw7rrHdO0zbI3L/86c50tam7X+ja2SpZF9/n5OEw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References:From:To: Cc:Date:Subject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector; b=s++3AGjsQnVbIGQLhDbZBiSOydRp+FZXYAp9skGL7sX3+xlawULsL2mHGalOsOe7M cWHHrOs1NvtnEMtlpzROumfkFlSo1jPMPFJO725zU1q0IJ0RSEGqdW+WD6nwIh750P MFnPnOjjRQsHI74inu1YuL4Q6RhdhAd/tmmyjS3y26rdGlSufSRAnGlmW7tPu0G57E XkCFNw9YLMOzmJVik29EUUmAQeY6f2LfnYfNezLzgAX4Md8DxYh9gptXeqiIj/eywM h4DCKi+kaCGERSo+r24v6MZA27NucfjNO0bsy3V5f3YETPteI80YhUtikMgN/VsUFg Zq8gU8WVKG9OA== X-Pm-Submission-Id: 4gRkxn54VVz1DDKv From: =?UTF-8?q?Onur=20=C3=96zkan?= To: rcu@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Cc: ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, peterz@infradead.org, fujita.tomonori@gmail.com, tamird@kernel.org, jiangshanlai@gmail.com, paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, =?UTF-8?q?Onur=20=C3=96zkan?= Subject: [PATCH v9 2/4] srcu: expose srcu_readers_active() Date: Fri, 29 May 2026 16:39:52 +0300 Message-ID: <20260529134004.396743-3-work@onurozkan.dev> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260529134004.396743-1-work@onurozkan.dev> References: <20260529134004.396743-1-work@onurozkan.dev> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is needed by rust/helpers/srcu.c which now adds rust_helper_srcu_readers_active() as a wrapper around the SRCU helper for Rust callers. To achive this: 1- Move the srcu_readers_active() implementation from "kernel/rcu/srcutree.c" to "include/linux/srcutree.h". 2- Implement a matching srcu_readers_active() in "include/linux/srcutiny.h" and use it on the existing open-coded WARN_ON() check in cleanup_srcu_struct(). Reviewed-by: Gary Guo Reviewed-by: Paul E. McKenney Signed-off-by: Onur Özkan --- include/linux/srcutiny.h | 13 +++++++++++++ include/linux/srcutree.h | 24 ++++++++++++++++++++++++ kernel/rcu/srcutiny.c | 2 +- kernel/rcu/srcutree.c | 25 ------------------------- rust/helpers/srcu.c | 5 +++++ 5 files changed, 43 insertions(+), 26 deletions(-) diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 905b629e8fa3..fbcf13bc12d1 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -154,4 +154,17 @@ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, data_race(READ_ONCE(ssp->srcu_idx_max))); } +/** + * srcu_readers_active - returns true if there are readers. and false otherwise. + * @ssp: which srcu_struct to count active readers (holding srcu_read_lock). + * + * Note that this is not an atomic primitive, and can therefore suffer + * severe errors when invoked on an active srcu_struct. That said, it + * can be useful as an error check at cleanup time. + */ +static inline bool srcu_readers_active(struct srcu_struct *ssp) +{ + return READ_ONCE(ssp->srcu_lock_nesting[0]) || READ_ONCE(ssp->srcu_lock_nesting[1]); +} + #endif diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index fd1a9270cb9a..75e54e4f963f 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -374,4 +374,28 @@ static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flav __srcu_check_read_flavor(ssp, read_flavor); } +/** + * srcu_readers_active - returns true if there are readers. and false otherwise. + * @ssp: which srcu_struct to count active readers (holding srcu_read_lock). + * + * Note that this is not an atomic primitive, and can therefore suffer + * severe errors when invoked on an active srcu_struct. That said, it + * can be useful as an error check at cleanup time. + */ +static inline bool srcu_readers_active(struct srcu_struct *ssp) +{ + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); + + sum += atomic_long_read(&sdp->srcu_ctrs[0].srcu_locks); + sum += atomic_long_read(&sdp->srcu_ctrs[1].srcu_locks); + sum -= atomic_long_read(&sdp->srcu_ctrs[0].srcu_unlocks); + sum -= atomic_long_read(&sdp->srcu_ctrs[1].srcu_unlocks); + } + return sum; +} + #endif diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 780a95e8cad7..dde99876d473 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -85,7 +85,7 @@ EXPORT_SYMBOL_GPL(init_srcu_struct_generic); */ void cleanup_srcu_struct(struct srcu_struct *ssp) { - WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]); + WARN_ON(srcu_readers_active(ssp)); irq_work_sync(&ssp->srcu_irq_work); flush_work(&ssp->srcu_work); WARN_ON(ssp->srcu_gp_running); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 45154630c54e..d1a69320b5c0 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -599,31 +599,6 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) return srcu_readers_lock_idx(ssp, idx, did_gp, unlocks); } -/** - * srcu_readers_active - returns true if there are readers. and false - * otherwise - * @ssp: which srcu_struct to count active readers (holding srcu_read_lock). - * - * Note that this is not an atomic primitive, and can therefore suffer - * severe errors when invoked on an active srcu_struct. That said, it - * can be useful as an error check at cleanup time. - */ -static bool srcu_readers_active(struct srcu_struct *ssp) -{ - int cpu; - unsigned long sum = 0; - - for_each_possible_cpu(cpu) { - struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); - - sum += atomic_long_read(&sdp->srcu_ctrs[0].srcu_locks); - sum += atomic_long_read(&sdp->srcu_ctrs[1].srcu_locks); - sum -= atomic_long_read(&sdp->srcu_ctrs[0].srcu_unlocks); - sum -= atomic_long_read(&sdp->srcu_ctrs[1].srcu_unlocks); - } - return sum; -} - /* * We use an adaptive strategy for synchronize_srcu() and especially for * synchronize_srcu_expedited(). We spin for a fixed time period diff --git a/rust/helpers/srcu.c b/rust/helpers/srcu.c index 225b3bf9334a..1a2f563640e0 100644 --- a/rust/helpers/srcu.c +++ b/rust/helpers/srcu.c @@ -9,6 +9,11 @@ __rust_helper int rust_helper_init_srcu_struct_with_key(struct srcu_struct *ssp, return __init_srcu_struct(ssp, name, key); } +__rust_helper bool rust_helper_srcu_readers_active(struct srcu_struct *ssp) +{ + return srcu_readers_active(ssp); +} + __rust_helper int rust_helper_srcu_read_lock(struct srcu_struct *ssp) { return srcu_read_lock(ssp); -- 2.51.2