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 CAC9A15B13A for ; Mon, 5 Aug 2024 15:59:47 +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=1722873589; cv=none; b=TSy8DvvyxWSh22L5Tq4UlqHSx78r8mxrBY29vyT2Hy+M0mrcuI96Bgw9ZTD7tJjC+oE92p7c0//aGlMJTTqy+Aj2r283ZI9dVvJmLGYwSbkz8tb82tT5XHaZwIy/0dJYclpel9BjYVAVFjmkMOQrZmhLzbUW01MgW2117g1DdtE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722873589; c=relaxed/simple; bh=q73GkdMAUsuhmAurIE+4Rh4oA3WCaPz5k88nx2PWlUQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Va3wagHS701w7JrzZXpLgPq3y2DhAHH55J433r3arVrQfFAYE3A6upF5F5KIiH/k7/PKKa6lfRBKSD/zFznVOVer0Gngw7ue0+Ac5Vq+Mgbm9no6bIoVOYG7bvaYV/rs4os3gpe8x5UJ30z2XcYrV83ETxphI3YRkYPH1Q/aQOY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=AOH3DJeT; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="AOH3DJeT" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722873586; 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=F5WoF7SpMgNw9Tt7F4AdxuqhGssiOGa0SxaZrKFwOpc=; b=AOH3DJeT//Li3jMDTPWCjoxYsqU3H9TBQl7Tmc+IaVQL7X4i4oZhO4MxEbT4Lk5FWqQwby uCuO+ZthIG0A4iBpsCaEIW/HJieSgl/6sAQCl9EIgKlA+5ST6uUTSF5m9gz+dxMYP7Ck3k K/zaLHTWv/SGaUQKH79SJJxQ18xiL5s= Received: from mx-prod-mc-01.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-63-MA47QDb7PJSsHtxBMgmnig-1; Mon, 05 Aug 2024 11:59:40 -0400 X-MC-Unique: MA47QDb7PJSsHtxBMgmnig-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8A1B11955D52; Mon, 5 Aug 2024 15:59:38 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.34]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 9BA311955D44; Mon, 5 Aug 2024 15:59:34 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 5 Aug 2024 17:59:36 +0200 (CEST) Date: Mon, 5 Aug 2024 17:59:32 +0200 From: Oleg Nesterov To: Andrii Nakryiko Cc: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org Subject: Re: [PATCH 5/8] uprobes: travers uprobe's consumer list locklessly under SRCU protection Message-ID: <20240805155931.GC11049@redhat.com> References: <20240731214256.3588718-1-andrii@kernel.org> <20240731214256.3588718-6-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-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: <20240731214256.3588718-6-andrii@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On 07/31, Andrii Nakryiko wrote: > > @@ -1120,17 +1098,19 @@ void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc) > int err; > > down_write(&uprobe->register_rwsem); > - if (WARN_ON(!consumer_del(uprobe, uc))) { > - err = -ENOENT; OK, I agree, this should never happen. But if you remove this check, then > int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool add) > { > struct uprobe_consumer *con; > - int ret = -ENOENT; > + int ret = -ENOENT, srcu_idx; > > down_write(&uprobe->register_rwsem); > - for (con = uprobe->consumers; con && con != uc ; con = con->next) > - ; > - if (con) > - ret = register_for_each_vma(uprobe, add ? uc : NULL); > + > + srcu_idx = srcu_read_lock(&uprobes_srcu); > + list_for_each_entry_srcu(con, &uprobe->consumers, cons_node, > + srcu_read_lock_held(&uprobes_srcu)) { > + if (con == uc) { > + ret = register_for_each_vma(uprobe, add ? uc : NULL); > + break; > + } > + } we can probably remove the similar check above? I mean, why do we need the list_for_each_entry_srcu() above? Is it possible that uprobe_apply(uprobe, uc) is called when "uc" is not on the ->consumers list? At first glance I see no problems in this patch... but you know, my eyes are already blurring, I'll continue tomorrow and read this patch again. Oleg.