From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 115FE25D1E9 for ; Thu, 26 Feb 2026 14:04:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772114682; cv=none; b=i6YPWQRqp+vyVdawz7RZ/LNT7HNQO5ETufUPtheg4vLiVcAsemHmZmqQYj9f/EsfsL7ggyCD47qBM/n+6ZR5UsjkrboMN8yYQ/pZnINRthjQj7LoNW+8ixHKjKZ6hA31PtbG5K4hkRH3OsrE4Oba7co+Up4ZNDF6Iv8GF+CGwmg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772114682; c=relaxed/simple; bh=ZPrfuNnO1n8ODYByKlvzs1rczBFGZ/IjALAS+Uul6Zk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JF02f95Sk5tVKqon0OZ4R+ieJ+BKcO+h3M0Uax7xWl3V4YEGO3XiEU7ePQfHSmzA8HoMPO3F0PGnfo0oyQ2d5H0uy00iYIXq2LaI5R2/hIMDQOmEm8QGwZUSObRo64ZPWLdFVr60ALEeh2YkKy3BASUEoOzxCZ3zP7BYeLuYScY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=VZRhCRrg; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VZRhCRrg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772114680; 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=nGVLntgS7y17jrtUPVq3eOV3I3Dp+Pz66Cj+hxDGxis=; b=VZRhCRrgS+R9GpmMml3L2Cc5c4PBTN+61jNcYczIuMDYCKqS7dhf1bHGQTwVE4pI6FoZvr JAeSiEeXHorHjQ7nhoq2YSjLjMg1aUm/Xf1lAfCgbnkN8kYmJm18KtmLKGTRkB1QjKYqJ6 CU5tmocy2ebtGljlDjkYFmTm8KeaO58= Received: from mx-prod-mc-03.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-441-cd0trrkZNFKZDEH-N7NXbA-1; Thu, 26 Feb 2026 09:04:37 -0500 X-MC-Unique: cd0trrkZNFKZDEH-N7NXbA-1 X-Mimecast-MFC-AGG-ID: cd0trrkZNFKZDEH-N7NXbA_1772114675 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ED52D1956079; Thu, 26 Feb 2026 14:04:34 +0000 (UTC) Received: from fedora (unknown [10.72.116.93]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0EE591956053; Thu, 26 Feb 2026 14:04:25 +0000 (UTC) Date: Thu, 26 Feb 2026 22:04:18 +0800 From: Ming Lei To: Daniel Wagner Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Guangwu Zhang , Chengming Zhou , Thomas Gleixner , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 3/3] Revert "lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly" Message-ID: References: <20260226-revert-cpu-read-lock-v1-0-eb005072566e@kernel.org> <20260226-revert-cpu-read-lock-v1-3-eb005072566e@kernel.org> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260226-revert-cpu-read-lock-v1-3-eb005072566e@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On Thu, Feb 26, 2026 at 02:40:37PM +0100, Daniel Wagner wrote: > This reverts commit 0263f92fadbb9d294d5971ac57743f882c93b2b3. > > The reason the lock was removed was that the nvme-pci driver reset > handler attempted to acquire the CPU read lock during CPU hotplug > offlining (holds the CPU write lock). Consequently, the block layer > offline notifier callback could not progress because in-flight requests > were detected. > > Since then, in-flight detection has been improved, and the nvme-pci > driver now explicitly updates the hctx state when it is safe to ignore > detected in-flight requests. As a result, it's possible to reintroduce > the CPU read lock in group_cpus_evenly. Can you explain your motivation a bit? Especially adding back the lock causes the API hard to use. Any benefit? Thanks, Ming