From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from va-1-115.ptr.blmpb.com (va-1-115.ptr.blmpb.com [209.127.230.115]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E87923EAB3 for ; Thu, 19 Mar 2026 03:03:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.127.230.115 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773889384; cv=none; b=SEcYn0U9Cc2bUhFVZAU1O3F59gdE5X3VAPv4dHs2Beu36k0Fe9AHt0v+elf4KPK4h6lw77KT4ihU+egIjz29iBgy51b2IioE1pneLyT9hVv01al5VAJZLWc2j+zfO9+U4G95oMfBgX5dSnXS3A05WgaDGegj9ExmjA2T+z3y26g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773889384; c=relaxed/simple; bh=xupKtGlpy8cMAqQg6SRCjCSf0Af5UBeZBDgtesyN0Ec=; h=Mime-Version:References:Cc:Message-Id:Subject:From:Content-Type: In-Reply-To:To:Date; b=MM9FdKNoH3GfDHA1cXf6vfseZyYzbSs0l3qEGU7TfxRgBC3Z2Oh4B9781l7NcMAU3Eu7nDeR9EUMhjfYy6GfTxsaKrLAXGTkWPBbTJ9lNB2s2G4IC6SZIao5uxiGBxs1WiiJ/Xe06/SV39JGnl+Q2kPM9UHfvXapmIUrglhZbCg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=jMoWJM0C; arc=none smtp.client-ip=209.127.230.115 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="jMoWJM0C" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=2212171451; d=bytedance.com; t=1773889370; h=from:subject: mime-version:from:date:message-id:subject:to:cc:reply-to:content-type: mime-version:in-reply-to:message-id; bh=xupKtGlpy8cMAqQg6SRCjCSf0Af5UBeZBDgtesyN0Ec=; b=jMoWJM0CBE+ysQyGd8zTQ12Lvi1eqMuyCtnJ2KHKlkiz/omU3b9PM+e4MoaUCFmu+nYnrR qU2QXsjJRQKZg0M2eLpTwDPO0k2ug+qrG6w6MprEIqFY1cgKDoLImHR71rNjLZnQp/V7R4 TsP6TXlyQKHTvKyAF3yGBxomTZePOgeydm6yIi6UeT2DJVbFMR53MHUxI6hn6PiqbmCEVQ VMxvS51FBGQqB3UGUTjJsjYuMO72NNiX1rDGKndwKX30qBIXWrS+m1gEs5f9m4BwkU4rSR WsPQjhknO4y2L7mkVJ6YE/NBBT/bcDeqsmLDflywYtSHYdlT20J0G4SAvHJ7xA== Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Original-From: Chuyi Zhou References: <20260318045638.1572777-1-zhouchuyi@bytedance.com> <20260318045638.1572777-5-zhouchuyi@bytedance.com> <20260318155552.41ffiYbB@linutronix.de> Cc: , , , , , , , , , , , Message-Id: <08bf0239-4b4c-43e8-8384-05dcc29f9152@bytedance.com> Subject: Re: [PATCH v3 04/12] smp: Use on-stack cpumask in smp_call_function_many_cond X-Lms-Return-Path: From: "Chuyi Zhou" Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 In-Reply-To: <20260318155552.41ffiYbB@linutronix.de> User-Agent: Mozilla Thunderbird To: "Sebastian Andrzej Siewior" Date: Thu, 19 Mar 2026 11:02:32 +0800 Hi Sebastian, =E5=9C=A8 2026/3/18 23:55, Sebastian Andrzej Siewior =E5=86=99=E9=81=93: > On 2026-03-18 12:56:30 [+0800], Chuyi Zhou wrote: >> This patch use on-stack cpumask to replace percpu cfd cpumask in >> smp_call_function_many_cond(). Note that when both CONFIG_CPUMASK_OFFSTA= CK >> and PREEMPT_RT are enabled, allocation during preempt-disabled section >> would break RT. Therefore, only do this when CONFIG_CPUMASK_OFFSTACK=3Dn= . >> This is a preparation for enabling preemption during csd_lock_wait() in >> smp_call_function_many_cond(). >=20 > You explained why we do this only for !CONFIG_CPUMASK_OFFSTACK but > failed to explain why we need a function local cpumask. Other than > preparation step. But this allocation looks pointless, let me look > further=E2=80=A6 >=20 OK. It might be better to explain here why we need an local cpumask. Thanks. >> Signed-off-by: Chuyi Zhou >> Reviewed-by: Muchun Song >=20 > Sebastian