From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41BE8CCD18E for ; Mon, 13 Oct 2025 15:55:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:To:From:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wVWnS0RcSrifKORRkaxSlEBfAdbDlyJkXOwnKgyyCWE=; b=r0VppuYpL4MUSL dYGtOa+OqHog4YWh7VJyyaehficEh70YMNriLC7Oq64lRcEbf/c6IO8Z3o6uccQ4C0DjD8ZNkDC1Z v0kvbJ5dy6n7RF76yztkUaDovEHmx+WRVXT9HrLvF0mLO8uLBB0/FpkwNU2xXS+/Dg7/S4oI4t+2g c2IlrmixuUOViuGT9tYWFkDEwKLB2KlhsU/7b0d1ocJtFhuEbgh2o0Ple+PnCLaRjbTEA21Iqgq4W Os+BIBz+v+sM1wT3jIZDxIuLw3oybPVXMNao93GffiaosVRxi0qke9Tz/fOv7jRp2zUDFrhZRTYnN MIPGbysJVRNbgo0MPLsQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8Ktg-0000000DltZ-1wRP; Mon, 13 Oct 2025 15:55:40 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8Ktd-0000000Dlse-309K for linux-arm-kernel@lists.infradead.org; Mon, 13 Oct 2025 15:55:38 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760370936; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wVWnS0RcSrifKORRkaxSlEBfAdbDlyJkXOwnKgyyCWE=; b=Wr0XILPrG6efWVPsQFrqzO0zfu2JJ0xRuU4+OJoUK2/xqFjXCV2a6OSP3Mn6q7HSQIJxcl kR+hyiaZdJhZVRIiEEfoi1Bce7A3YEk8WljkdqkeMgCKSIEqfMGyaJltgnjzowcDsKZFHO dL2zg0aUDD22xcwPx2yIp78fGR0Dn3c= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-104-hoQr19x9MGeShnhZzexXCg-1; Mon, 13 Oct 2025 11:54:05 -0400 X-MC-Unique: hoQr19x9MGeShnhZzexXCg-1 X-Mimecast-MFC-AGG-ID: hoQr19x9MGeShnhZzexXCg_1760370842 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D86331954105; Mon, 13 Oct 2025 15:54:01 +0000 (UTC) Received: from chopper.lan (unknown [10.22.81.1]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9BC8E30002D0; Mon, 13 Oct 2025 15:53:56 +0000 (UTC) From: Lyude Paul To: rust-for-linux@vger.kernel.org, Thomas Gleixner , Boqun Feng , linux-kernel@vger.kernel.org, Daniel Almeida Subject: [PATCH v13 04/17] preempt: Introduce __preempt_count_{sub, add}_return() Date: Mon, 13 Oct 2025 11:48:06 -0400 Message-ID: <20251013155205.2004838-5-lyude@redhat.com> In-Reply-To: <20251013155205.2004838-1-lyude@redhat.com> References: <20251013155205.2004838-1-lyude@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251013_085537_866030_12396006 X-CRM114-Status: GOOD ( 14.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juergen Christ , "open list:S390 ARCHITECTURE" , "maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" , "open list:GENERIC INCLUDE/ASM HEADER FILES" , Arnd Bergmann , Vasily Gorbik , Catalin Marinas , Heiko Carstens , Dave Hansen , Uros Bizjak , Brian Gerst , Ingo Molnar , Borislav Petkov , Sven Schnelle , "H. Peter Anvin" , Alexander Gordeev , Christian Borntraeger , Will Deacon , Jinjie Ruan , "moderated list:ARM64 PORT AARCH64 ARCHITECTURE" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Boqun Feng In order to use preempt_count() to tracking the interrupt disable nesting level, __preempt_count_{add,sub}_return() are introduced, as their name 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, flags); } Having these primitives will avoid a read of preempt_count() after changing preempt_count() on certain architectures. Signed-off-by: Boqun Feng --- V10: * Add commit message I forgot * Rebase against latest pcpu_hot changes V11: * Remove CONFIG_PROFILE_ALL_BRANCHES workaround from __preempt_count_add_return() arch/arm64/include/asm/preempt.h | 18 ++++++++++++++++++ arch/s390/include/asm/preempt.h | 10 ++++++++++ arch/x86/include/asm/preempt.h | 10 ++++++++++ include/asm-generic/preempt.h | 14 ++++++++++++++ 4 files changed, 52 insertions(+) diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index 932ea4b620428..0dd8221d1bef7 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -55,6 +55,24 @@ 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 6ccd033acfe52..5ae366e26c57d 100644 --- a/arch/s390/include/asm/preempt.h +++ b/arch/s390/include/asm/preempt.h @@ -98,6 +98,16 @@ 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 578441db09f0b..1220656f3370b 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 51f8f3881523a..c8683c046615d 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) { /* -- 2.51.0