From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 2CB782FD668 for ; Tue, 2 Dec 2025 07:29:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764660585; cv=none; b=cMwrduNK6VNLPx0Ocfxl6p3OiERUpSVR6PSTo5+v3uc41cEtiFOVCHFws5tins8f4tFrOdN13b2o3ZkIDeZ+ikM0xJPl8pWh3PVpk68thxiEk5iI6AJoX+cwrqy2IaMlJ1H4Wgv/aRYdut6/9o6/Vw3eB/iieYWy4w2+mMYingw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764660585; c=relaxed/simple; bh=LxTGsAT8S7ai4M5EiSZkbRd+mM5VhH7A9YWPMv6Ge6U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DHD36LYNvFrS2V9HTx8XM9LD29dL8m6HE2BVfxknVjnToj9stZDUcWEdB+lkFX/qrrApArsKEXfK8guiBdC2PHvG3OJ0cfuTEataAjLfH4QcpsQhtc7nCf+Dgwt/tSqttg0IHHyuoBf7w5NWZrKLxO8GKTIM8qv9p4/lhgb6Tro= 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=d+KLG/ef; arc=none smtp.client-ip=170.10.133.124 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="d+KLG/ef" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764660583; 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=wQop+DCjNpoHFIhrNY2xS0U6iO9hNt8qs85RvlXH09Q=; b=d+KLG/efo6f027D8DI6T0aWHjcsiDVXTuz7xxOXSG5rnjix/gUBFQx6Bg6YxpM6dyIoN4/ mLrxTcBMLLnBy5uh8w94SCc9bCyBDDBbZxAEB6no3UtOZVqSvCEhCg6TDDYnkXQuHVXrR+ Rd4kNqBFFjHcGLfuzzFnYxKM9R0t26s= Received: from mx-prod-mc-05.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-262-c7qjTuXbOr-QEGIZYVoO7Q-1; Tue, 02 Dec 2025 02:29:39 -0500 X-MC-Unique: c7qjTuXbOr-QEGIZYVoO7Q-1 X-Mimecast-MFC-AGG-ID: c7qjTuXbOr-QEGIZYVoO7Q_1764660578 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ABF2F1956095; Tue, 2 Dec 2025 07:29:38 +0000 (UTC) Received: from fedora (unknown [10.45.224.180]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 2651219560A7; Tue, 2 Dec 2025 07:29:36 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 2 Dec 2025 08:29:38 +0100 (CET) Date: Tue, 2 Dec 2025 08:29:35 +0100 From: Oleg Nesterov To: Ingo Molnar Cc: Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] seqlock, procfs: Fix scoped_seqlock_read() critical section in do_task_stat() Message-ID: References: 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: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 12/02, Ingo Molnar wrote: > > RCU read-lock should not nest inside a read-seqlock > irqsave ->stats_lock IRQs-off critical section, Hmm... I agree with this patch, but is it actually wrong? I thought that rcu_read_lock/unlock is safe under spin_lock_irq... > + { > + guard(rcu)(); > + scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) { how about scoped_guard(rcu) { scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) { ... } } ? Oleg.