From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 0235C221FDC for ; Tue, 8 Jul 2025 06:51:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751957489; cv=none; b=Qq3qoSwLYOUAvMSsspTWpq3EUchuTRsPgc8rFnUS1ZOo8NIzidp/ZY6nTrZ65N0Jv2Ky99RVALM+WUE3Pki2CRKkK+eEhcfqZOYbYSBN7UgP5CtCJRSGGfnG2JIj8x3jk7p0gx7EAMMsPwhb0c3yhJPB0HPrxYHLoJpAk1z8x7A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751957489; c=relaxed/simple; bh=PLfjNm3poT/pfKPoFgdKwOT2UOWmgK9Z01i+zwU6npI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=r3ekqlvGcdvOV3aBI/lUq9EIltoAEJJf7FuORu8geHJrIlpUdQtTttfydmyjFaIx7A48GCqsjgvSyDUP5KDb9Q1dxpKWBiq2PKzfhiehvO5TRFpum815VtYP0IplIqdH6MkwMdt7vTkihgSiGqdMZVOuSYtWbNVGwqBJlLxlPoo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=PJRubHV3; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=IaMNtKzJ; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="PJRubHV3"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="IaMNtKzJ" Date: Tue, 8 Jul 2025 08:51:24 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1751957485; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Mer2kyNEMt/0U4ldunFN9CzzxmGrd8ltq1fNYekIqfg=; b=PJRubHV3zGPPmouIO5pnqMt+usLPL5bBszusoIOz4UrbftfhyxnMsEIXphKmAMBUKaDWg0 9MNJe+S2U5vY2hDvXJ8/CE3P75NUvOlwc/g0EklN1jyPqnUXg5xE8ObOO3qpLIrSA0jSSY sEdPj0S3ke7EJziI0SYX+wXSlDkjNesIIfAHMmodXMArhoW9/6a7puaUmF4+yDO5c2JxKR MiolFUcp4YLtsZENCb9QfbBpCER7+A9VJi/DozLp01YdDWM+OYH/UWzY5d0wQXSrajx0xs 3u42beW1dp8AG/IfjjN8KLkFaEmFGmIU4e7fM90xb+b4bN6ih2TkVkvU2gUkHQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1751957485; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Mer2kyNEMt/0U4ldunFN9CzzxmGrd8ltq1fNYekIqfg=; b=IaMNtKzJt3PbQB9Sx1UfCay2FfWT19BX9Pre8Pn60/m/+B6a1RAaN5MoCyhBDB4l/+yUZ3 i202MzwIXi7GdbAA== From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: =?utf-8?B?QW5kcsOp?= Almeida , Darren Hart , Davidlohr Bueso , Ingo Molnar , Juri Lelli , Peter Zijlstra , Thomas Gleixner , Valentin Schneider , Waiman Long Subject: Re: [PATCH 2/3] futex: Use RCU-based per-CPU reference counting instead of rcuref_t Message-ID: <20250708065124.DtoAH-O1@linutronix.de> References: <20250707143623.70325-1-bigeasy@linutronix.de> <20250707143623.70325-3-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250707143623.70325-3-bigeasy@linutronix.de> On 2025-07-07 16:36:22 [+0200], To linux-kernel@vger.kernel.org wrote: > From: Peter Zijlstra > > The use of rcuref_t for reference counting introduces a performance bottleneck > when accessed concurrently by multiple threads during futex operations. just folded this bit after kernel test robot complained: diff --git a/include/linux/futex.h b/include/linux/futex.h index cd773febd497b..9e9750f049805 100644 --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -113,7 +113,7 @@ static inline int futex_hash_allocate_default(void) return 0; } static inline int futex_hash_free(struct mm_struct *mm) { return 0; } -static inline void futex_mm_init(struct mm_struct *mm) { } +static inline int futex_mm_init(struct mm_struct *mm) { return 0; } #endif Sebastian