From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E01A8474278 for ; Tue, 4 Aug 2026 16:15:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785860110; cv=none; b=uoNmu6FCq/Ze88k+0W/qu53Ihck/xDeZEgPZhMjit3avGPgtv7pSS9XXodRWOcU4JI2u1ljU6BP5wfx4rBBU97gke2nmsZqIKUaLcD23qMFeeautnCvkifSnWdmhG+wxc/d+xyAiPwRH7P4gO+pbj/9E6xQqnASd6HcphwvYSEI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785860110; c=relaxed/simple; bh=ZdmP9HCAd2oDU8aGybcrgEt64oPFu3q8ZuAOXbDuT/Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ICxldl+lE0MBZDkhb6/HZfZgae7EN+KSoIf6msqUsBT0LxZFBAggKyO8zWy9PzbMElA1Rx9y1U7CN/eW/xCRv8ERkiZz3lT0fUFlQvrwtrj9PwJi3F+eMOdQhaIEd3yqW6NtMEJoKNvpaSngVe4Q4ZXlGX7Y4XnugdSS/BH31W4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L+dHwV53; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="L+dHwV53" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E72AC1F00ACF; Tue, 4 Aug 2026 16:15:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785860101; bh=4/3Q4RbdeBoEcapTLQLRtJHDgKIOcLItV3asUF3+BOc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=L+dHwV53qP3k4wqLoSjUkrebLPJGSMNKOhTywAQQ76uECjB9szMD30Fck+oG19BQr vYFOU8xOUhiA3cVrRiA7OXhQvtzqYGMHRpMDBTFfzSMxFcdl+0RDCO6etVU6iTPQrP T/Bxvrxk5mz82p3Pfpn6J6Vszci/sWc89Ye1DtAUe6dCDnFuqk9Qh4AHDfX6sN0voA s0iu432/ah2rvpTk91k7WL9lBpZvBFecycd19POrbWL7yU8pk7pSOM6rbWl9qkjYxd +b2shnkLbbQJJJF+9mwiJPa/G/yp6a+Xaqr5P9b1zL6ASGq2XLPj8nlNynXg55D/2R CsIyERxBD5jDQ== Received: from phl-compute-02.internal (phl-compute-02.internal [10.202.2.42]) by mailfauth.phl.internal (Postfix) with ESMTP id E9FDCF40066; Tue, 4 Aug 2026 12:14:59 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-02.internal (MEProxy); Tue, 04 Aug 2026 12:14:59 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTEjNALs/vHMOloma/FioWgq38LEDphqLbi/MDKjZ+skyek9CBm72qNR6fF0uZPdGp TNcnAR4AQwTabPyqXb4b8VVQVFCNoT48fsLJV/4jNEVJ0A9eFv0ovpeauV2dgztP0aY1Y0 jIaZAzpZKJmSr5bjx5yubrqLJ++dH6uDgWLI4XXVkSa8jJqAXQgEQlXOv7WGccuHPTRlER Ylu8rJket0jbyQhGWZ+weYiCIeD4wr9LDagDzAHrKU27qzYbzXZIXOYWeFfQKFS5QVbMSU NlfDPJ2QDHkDrdBA1iUAq2dsmA2mOrsNEsIEQsqJKBWsANZHLO8XMG8BasrOULdBqAdbXq 8UWtW5wdOgo9aU+rtxQ2MCFvpZ1+bx4h2YQzeYk5x0rFmmR478XZgVEan5718CRZzA7cJT RnYvxUiw3FBCFcKLF2ObIgX5tCyLTffdBvXgpfd+ITNATyzuAOQjd2N7q6QQrhazVXBuQ0 BOeytv+jFZQRffaNB2xUY8b3dffI+MBCzSsfVl7RL8OrRxgsLZ42l9oG/k+CZG9SKM1euD oLOt+3vFBxammBZr9RVXSajzGnXVlKJ4w1X2c3v/RI0Amg5PnYNtD7xpOsjyGHf3LWXSoS Oqb68hADFB8Akot3opT/e9JRdvh79gPT8zgMBkNQb93oLl3h6L9XkT20cf5g X-ME-Proxy: Feedback-ID: i8dbe485b:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 4 Aug 2026 12:14:59 -0400 (EDT) From: Boqun Feng To: Peter Zijlstra Cc: "Ingo Molnar" , "Will Deacon" , "Boqun Feng" , "Waiman Long" , "Gary Guo" , "Alice Ryhl" , "Lyude Paul" , "Daniel Almeida" , =?UTF-8?q?Onur=20=C3=96zkan?= , "Miguel Ojeda" , "Danilo Krummrich" , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Heiko Carstens Subject: [PATCH v4 03/17] preempt: Introduce __preempt_count_{sub,add}_return() Date: Tue, 4 Aug 2026 09:14:25 -0700 Message-ID: <20260804161447.84806-4-boqun@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260804161447.84806-1-boqun@kernel.org> References: <20260804161447.84806-1-boqun@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In order to use preempt_count() to track the interrupt disable nesting level, __preempt_count_{add,sub}_return() are introduced, as their names suggest, these primitives return the new value of the preempt_count() after changing it. The following example shows the usage of it in local_interrupt_disable(): // increase the HARDIRQ_DISABLE bit new_count = __preempt_count_add_return(HARDIRQ_DISABLE_OFFSET); // if it's the first-time increment, then disable the interrupt // at hardware level. if ((new_count & HARDIRQ_DISABLE_MASK) == HARDIRQ_DISABLE_OFFSET) { local_irq_save(flags); raw_cpu_write(local_interrupt_disable_state, flags); } Having these primitives will avoid a read of preempt_count() after changing preempt_count() on certain architectures. Acked-by: Heiko Carstens # s390 Signed-off-by: Boqun Feng --- arch/arm64/include/asm/preempt.h | 20 ++++++++++++++++++++ arch/s390/include/asm/preempt.h | 10 ++++++++++ arch/x86/include/asm/preempt.h | 10 ++++++++++ include/asm-generic/preempt.h | 14 ++++++++++++++ 4 files changed, 54 insertions(+) diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index 932ea4b62042..9ecc2766a9f2 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -55,6 +55,26 @@ static inline void __preempt_count_sub(int val) WRITE_ONCE(current_thread_info()->preempt.count, pc); } +static inline int __preempt_count_add_return(int val) +{ + u32 pc = READ_ONCE(current_thread_info()->preempt.count); + + pc += val; + WRITE_ONCE(current_thread_info()->preempt.count, pc); + + return pc; +} + +static inline int __preempt_count_sub_return(int val) +{ + u32 pc = READ_ONCE(current_thread_info()->preempt.count); + + pc -= val; + WRITE_ONCE(current_thread_info()->preempt.count, pc); + + return pc; +} + static inline bool __preempt_count_dec_and_test(void) { struct thread_info *ti = current_thread_info(); diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h index 6e5821bb047e..0a25d4648b4c 100644 --- a/arch/s390/include/asm/preempt.h +++ b/arch/s390/include/asm/preempt.h @@ -139,6 +139,16 @@ static __always_inline bool should_resched(int preempt_offset) return unlikely(READ_ONCE(get_lowcore()->preempt_count) == preempt_offset); } +static __always_inline int __preempt_count_add_return(int val) +{ + return val + __atomic_add(val, &get_lowcore()->preempt_count); +} + +static __always_inline int __preempt_count_sub_return(int val) +{ + return __preempt_count_add_return(-val); +} + #define init_task_preempt_count(p) do { } while (0) /* Deferred to CPU bringup time */ #define init_idle_preempt_count(p, cpu) do { } while (0) diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index 578441db09f0..1220656f3370 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -85,6 +85,16 @@ static __always_inline void __preempt_count_sub(int val) raw_cpu_add_4(__preempt_count, -val); } +static __always_inline int __preempt_count_add_return(int val) +{ + return raw_cpu_add_return_4(__preempt_count, val); +} + +static __always_inline int __preempt_count_sub_return(int val) +{ + return raw_cpu_add_return_4(__preempt_count, -val); +} + /* * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule * a decrement which hits zero means we have no preempt_count and should diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h index 51f8f3881523..c8683c046615 100644 --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -59,6 +59,20 @@ static __always_inline void __preempt_count_sub(int val) *preempt_count_ptr() -= val; } +static __always_inline int __preempt_count_add_return(int val) +{ + *preempt_count_ptr() += val; + + return *preempt_count_ptr(); +} + +static __always_inline int __preempt_count_sub_return(int val) +{ + *preempt_count_ptr() -= val; + + return *preempt_count_ptr(); +} + static __always_inline bool __preempt_count_dec_and_test(void) { /* -- 2.50.1 (Apple Git-155)