From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752439AbbDAI5w (ORCPT ); Wed, 1 Apr 2015 04:57:52 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:36222 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752133AbbDAI5q (ORCPT ); Wed, 1 Apr 2015 04:57:46 -0400 From: Aleksa Sarai To: tj@kernel.org, lizefan@huawei.com, mingo@redhat.com, peterz@infradead.org Cc: richard@nod.at, fweisbec@gmail.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Aleksa Sarai Subject: [PATCH v8 1/4] cgroups: use bitmask to filter for_each_subsys Date: Wed, 1 Apr 2015 19:57:18 +1100 Message-Id: <1427878641-5273-2-git-send-email-cyphar@cyphar.com> X-Mailer: git-send-email 2.3.5 In-Reply-To: <1427878641-5273-1-git-send-email-cyphar@cyphar.com> References: <1427878641-5273-1-git-send-email-cyphar@cyphar.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a new macro for_each_subsys_which that allows all enabled cgroup subsystems to be filtered by a bitmask, such that mask & (1 << ssid) determines if the subsystem is to be processed in the loop body (where ssid is the unique id of the subsystem). Also replace the need_forkexit_callback with two separate bitmasks for each callback to make (ss->{fork,exit}) checks unnecessary. Signed-off-by: Aleksa Sarai --- kernel/cgroup.c | 43 ++++++++++++++++++++++++++----------------- 1 file changed, 26 insertions(+), 17 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 29a7b2c..1d69a085 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -175,12 +175,14 @@ static DEFINE_IDR(cgroup_hierarchy_idr); */ static u64 css_serial_nr_next = 1; -/* This flag indicates whether tasks in the fork and exit paths should +/* + * These bitmask flags indicate whether tasks in the fork and exit paths should * check for fork/exit handlers to call. This avoids us having to do * extra work in the fork/exit path if none of the subsystems need to * be called. */ -static int need_forkexit_callback __read_mostly; +static int need_fork_callback __read_mostly; +static int need_exit_callback __read_mostly; static struct cftype cgroup_dfl_base_files[]; static struct cftype cgroup_legacy_base_files[]; @@ -409,6 +411,19 @@ static int notify_on_release(const struct cgroup *cgrp) for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \ (((ss) = cgroup_subsys[ssid]) || true); (ssid)++) +/** + * for_each_subsys_which - filter for_each_subsys with a bitmask + * @ss_mask: the bitmask + * @ss: the iteration cursor + * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end + * + * The block will only run for cases where the ssid-th bit (1 << ssid) of + * mask is set to 1. + */ +#define for_each_subsys_which(ss_mask, ss, ssid) \ + for_each_subsys((ss), (ssid)) \ + if ((ss_mask) & (1 << (ssid))) + /* iterate across the hierarchies */ #define for_each_root(root) \ list_for_each_entry((root), &cgroup_roots, root_list) @@ -4932,7 +4947,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early) * init_css_set is in the subsystem's root cgroup. */ init_css_set.subsys[ss->id] = css; - need_forkexit_callback |= ss->fork || ss->exit; + need_fork_callback |= (bool) ss->fork << ss->id; + need_exit_callback |= (bool) ss->exit << ss->id; /* At system boot, before all subsystems have been * registered, no tasks have been forked, so we don't @@ -5239,11 +5255,8 @@ void cgroup_post_fork(struct task_struct *child) * css_set; otherwise, @child might change state between ->fork() * and addition to css_set. */ - if (need_forkexit_callback) { - for_each_subsys(ss, i) - if (ss->fork) - ss->fork(child); - } + for_each_subsys_which(need_fork_callback, ss, i) + ss->fork(child); } /** @@ -5287,16 +5300,12 @@ void cgroup_exit(struct task_struct *tsk) cset = task_css_set(tsk); RCU_INIT_POINTER(tsk->cgroups, &init_css_set); - if (need_forkexit_callback) { - /* see cgroup_post_fork() for details */ - for_each_subsys(ss, i) { - if (ss->exit) { - struct cgroup_subsys_state *old_css = cset->subsys[i]; - struct cgroup_subsys_state *css = task_css(tsk, i); + /* see cgroup_post_fork() for details */ + for_each_subsys_which(need_exit_callback, ss, i) { + struct cgroup_subsys_state *old_css = cset->subsys[i]; + struct cgroup_subsys_state *css = task_css(tsk, i); - ss->exit(css, old_css, tsk); - } - } + ss->exit(css, old_css, tsk); } if (put_cset) -- 2.3.4