From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 75E2243302F for ; Tue, 28 Jul 2026 12:39:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785242388; cv=none; b=LmcU3P04qsXrW/9ZsZ2x3Kz0+h+4QlvfkxBluUFzQoeFWSe+KGmLhmk8kTuknqqHpWKStW8uggXjfqK9V1/NT5kKn9Aqn9UcR052/BjGB2d4BD76zuLR0n+eVDDW94VAMRh4dMHQ3yd0paMP9reZqOXOzFjaYx6cAaqmicIN/Ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785242388; c=relaxed/simple; bh=pWV6z+z312qnQhlJKvuL2knNIVHFC+IiSIOeS+l3yo8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=BeEk8Tr7QZwRNcAkY3vHh5HkUIJIKx8K9Pz3SS7TX55X/G678VH6pJQ9saoWMosYdIJA1AIMpZy+oBw4DWd1rqDWGdmnlFl0fo5qxd5Mw44l6I+AHo6u6LHW982+uBOxLxQ95lTRRAiz2vgRJRU69ZlT5rG5MvymQtFPNXrg4i0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=mRQYazPb; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="mRQYazPb" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C8DD6175D; Tue, 28 Jul 2026 05:39:41 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 115513F86F; Tue, 28 Jul 2026 05:39:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785242385; bh=pWV6z+z312qnQhlJKvuL2knNIVHFC+IiSIOeS+l3yo8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mRQYazPbq72oSunmh6AVdfciE8lWRNEeSEHGp7Gcpoktx5MLCAKN5WaGtYL4tRYGO cvhyB9Mj4ljHJhr2mlCNAw1a/tSyi2ArfO06FpiRf6nU4YK5ZBW2v/QejfsPvw+2DK 4VOFxfpseuDtt473gvuQa39Xz8gQLJLMFdj7H9Xs= From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ada.coupriediaz@arm.com, ardb@kernel.org, catalin.marinas@arm.com, hca@linux.ibm.com, linux-kernel@vger.kernel.org, mark.rutland@arm.com, maz@kernel.org, peterz@infradead.org, ruanjinjie@huawei.com, vladimir.murzin@arm.com, will@kernel.org, yang@os.amperecomputing.com Subject: [RFC PATCH 02/13] arm64: preempt: Treat should_resched() as unlikely Date: Tue, 28 Jul 2026 13:38:48 +0100 Message-Id: <20260728123859.2911495-3-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20260728123859.2911495-1-mark.rutland@arm.com> References: <20260728123859.2911495-1-mark.rutland@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The arm64 implementation of should_resched() doesn't treat the need to resched as unlikely, while all other implementations do, e.g. * asm-generic since: bdb43806589096ac ("sched: Extract the basic add/sub preempt_count modifiers") * x86 since: c2daa3bed53a8117 ("sched, x86: Provide a per-cpu preempt_count implementation") * s390 since: c360192bf4a8dc72 ("s390/preempt: move preempt_count to the lowcore") Do the same for arm64. Signed-off-by: Mark Rutland Cc: Ada Couprie Diaz Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Jinjie Ruan Cc: Marc Zyngier Cc: Peter Zijlstra Cc: Vladimir Murzin Cc: Will Deacon Cc: Yang Shi --- arch/arm64/include/asm/preempt.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index ca2ad1a8db095..3ef24ab8f3399 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -58,7 +58,7 @@ static inline void __preempt_count_sub(int val) static inline bool should_resched(int preempt_offset) { u64 pc = READ_ONCE(current_thread_info()->preempt_count); - return pc == preempt_offset; + return unlikely(pc == preempt_offset); } static inline bool __preempt_count_dec_and_test(void) -- 2.30.2