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 68D5C3FFAC6 for ; Wed, 18 Mar 2026 15:55:56 +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=1773849363; cv=none; b=a8Yj9nOzjSMhIV50wsGGRvLM1VMnIatCwh7zy9h+IYxM2q6O9S+miefvBmV9Xyeu1EOS1NtA29+vfyUJzckNHJOGSWKwxLEAp2Izx2xfhS0vhyBqwXINr0pR0FMBTAJUIRaXYVenXBZceFMoe/Lj5o7D9E64cRVht25eNThD8tA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773849363; c=relaxed/simple; bh=/FhTWRqiFsfbkA2zCmUQNcyjCptyEegzaTO45Ig0OKA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZmYEnSJC+QVmZ/vbqqrf6a8IPbIBcKVTaxEvm5tXmJIzIgYIq6JAfeHco7HEzVRui811U6/BWjM8c1gGGAdGqzstTAMpVaAg8MaD2uqD5OqxuDYa0M/ywI1oa1cXpogBg5vkc3VrmBwmahrZ9iY3a6LGnm8Ht3tJzt/is5is94A= 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=Jb2AEs0K; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=DdSYhH9X; 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="Jb2AEs0K"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="DdSYhH9X" Date: Wed, 18 Mar 2026 16:55:52 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1773849354; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/FhTWRqiFsfbkA2zCmUQNcyjCptyEegzaTO45Ig0OKA=; b=Jb2AEs0KYBT5E4NMyme9tPjPfJyLA05ZSZI+jVq9lDcxABKRH7Nyprixn2Pa88/kM/Kdz5 tZuxGz/w+uVfAe+reg+jFl/uOmHoabWGWGCzLnpSgq5P9+772HikWaUES9ow16fWXubT10 QkGdOpbgmXw3iHSqW6+NILNRZ8Q3wnoh4XN6FlRw2IWwJl8rYmY007iBoIFlJFMa0QQMH/ CSqTX5rZhccc0hvyjPZt+uaiFrwvgbMIK8/sHUM/ogy0yijOa7jaLB5UBweyFWl6Cldw7l YdgeI6x/qek30LQTy1hcKLkkxrI3RlSQt8dhlQXUZKK/vzhtogmc9yFXlgaKcA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1773849354; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/FhTWRqiFsfbkA2zCmUQNcyjCptyEegzaTO45Ig0OKA=; b=DdSYhH9X9Ro2zLpsKVsRosXC90XxYuz0ejxfAI0xaxH6PwIxzCqxeUd4spUgwuttoBPDXK H4JL6TfOMm2YTuCg== From: Sebastian Andrzej Siewior To: Chuyi Zhou Cc: tglx@linutronix.de, mingo@redhat.com, luto@kernel.org, peterz@infradead.org, paulmck@kernel.org, muchun.song@linux.dev, bp@alien8.de, dave.hansen@linux.intel.com, pbonzini@redhat.com, clrkwllms@kernel.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 04/12] smp: Use on-stack cpumask in smp_call_function_many_cond Message-ID: <20260318155552.41ffiYbB@linutronix.de> References: <20260318045638.1572777-1-zhouchuyi@bytedance.com> <20260318045638.1572777-5-zhouchuyi@bytedance.com> 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 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20260318045638.1572777-5-zhouchuyi@bytedance.com> 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_OFFSTACK > 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(). 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 > Signed-off-by: Chuyi Zhou > Reviewed-by: Muchun Song Sebastian