Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753568Ab0KYALj (ORCPT ); Wed, 24 Nov 2010 19:11:39 -0500 Received: from smtp-out.google.com ([74.125.121.35]:32702 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752448Ab0KYALi convert rfc822-to-8bit (ORCPT ); Wed, 24 Nov 2010 19:11:38 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=dfPdX4sJG97kemsWYh/d7xcEzvpDblMQjGvHjXPonoQAQDpvVODKMAWmnebqo2SJER Bmkzze7mhCDN1VMuW7Qw== MIME-Version: 1.0 In-Reply-To: References: <1290577024-12347-1-git-send-email-ccross@android.com> Date: Wed, 24 Nov 2010 16:11:34 -0800 X-Google-Sender-Auth: uSI5zJtMgNZmMdHsbv0Ug75d3k8 Message-ID: Subject: Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup From: Colin Cross To: Paul Menage Cc: Li Zefan , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2270 Lines: 46 On Wed, Nov 24, 2010 at 3:54 PM, Paul Menage wrote: > On Tue, Nov 23, 2010 at 9:37 PM, Colin Cross wrote: >> @@ -364,12 +372,8 @@ static void __put_css_set(struct css_set *cg, int taskexit) >> ? ? ? ? ? ? ? ?struct cgroup *cgrp = link->cgrp; >> ? ? ? ? ? ? ? ?list_del(&link->cg_link_list); >> ? ? ? ? ? ? ? ?list_del(&link->cgrp_link_list); >> - ? ? ? ? ? ? ? if (atomic_dec_and_test(&cgrp->count) && >> - ? ? ? ? ? ? ? ? ? notify_on_release(cgrp)) { >> - ? ? ? ? ? ? ? ? ? ? ? if (taskexit) >> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set_bit(CGRP_RELEASABLE, &cgrp->flags); >> + ? ? ? ? ? ? ? if (atomic_dec_and_test(&cgrp->count)) >> ? ? ? ? ? ? ? ? ? ? ? ?check_for_release(cgrp); >> - ? ? ? ? ? ? ? } > > We seem to have lost some notify_on_release() checks - maybe move that > to check_for_release()? check_for_release immediately calls cgroup_is_releasable, which checks for the same bit as notify_on_release. There's no need for CGRP_RELEASABLE to depend on notify_on_release, or to check notify_on_release before calling check_for_release. >> ?/* Caller must verify that the css is not for root cgroup */ >> +void __css_get(struct cgroup_subsys_state *css, int count) >> +{ >> + ? ? ? atomic_add(count, &css->refcnt); >> + ? ? ? set_bit(CGRP_RELEASABLE, &css->cgroup->flags); >> +} > > Is css_get() the right place to be putting this? It's not clear to me > why a subsystem taking a refcount on a cgroup's state should render it > releasable when it drops that refcount. I matched the existing behavior, __css_put sets CGRP_RELEASABLE when refcnt goes to 0. > Should we maybe clear the CGRP_RELEASABLE flag right before doing the > userspace callback? Actually, I think CGRP_RELEASABLE can be dropped entirely. check_for_release is only called from __css_put, cgroup_rmdir, and __put_css_set (or free_css_set_work after my second patch). Those all imply that __css_get, get_css_set, or cgroup_create have been previously called, which are the functions that set CGRP_RELEASABLE. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/