Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751991AbbFFACh (ORCPT ); Fri, 5 Jun 2015 20:02:37 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:33107 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750836AbbFFACd (ORCPT ); Fri, 5 Jun 2015 20:02:33 -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 v13 1/5] cgroup: use bitmask to filter for_each_subsys Date: Sat, 6 Jun 2015 10:02:14 +1000 Message-Id: <1433548938-32560-1-git-send-email-cyphar@cyphar.com> X-Mailer: git-send-email 2.4.2 In-Reply-To: <1433547736-11707-1-git-send-email-cyphar@cyphar.com> References: <1433547736-11707-1-git-send-email-cyphar@cyphar.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4709 Lines: 130 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 --- include/linux/cgroup-defs.h | 2 ++ kernel/cgroup.c | 54 ++++++++++++++++++++++++++++----------------- 2 files changed, 36 insertions(+), 20 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 26d1cea..c5588c4 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -490,6 +490,8 @@ static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) #else /* CONFIG_CGROUPS */ +#define CGROUP_SUBSYS_COUNT 0 + static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {} static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {} diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0fd5227..5734717 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -178,12 +178,13 @@ 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 - * 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. +/* + * These bitmask flags indicate whether tasks in the fork and exit paths have + * fork/exit handlers to call. This avoids us having to do extra work in the + * fork/exit path to check which subsystems have fork/exit callbacks. */ -static int need_forkexit_callback __read_mostly; +static unsigned long have_fork_callback __read_mostly; +static unsigned long have_exit_callback __read_mostly; static struct cftype cgroup_dfl_base_files[]; static struct cftype cgroup_legacy_base_files[]; @@ -412,6 +413,25 @@ 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: the iteration cursor + * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end + * @ss_maskp: a pointer to the bitmask + * + * 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, ssid, ss_maskp) \ + if (!CGROUP_SUBSYS_COUNT) \ + ; \ + else \ + for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \ + if (((ss) = cgroup_subsys[ssid]) && false) \ + break; \ + else + /* iterate across the hierarchies */ #define for_each_root(root) \ list_for_each_entry((root), &cgroup_roots, root_list) @@ -4914,7 +4934,8 @@ 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; + have_fork_callback |= (bool)ss->fork << ss->id; + have_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 @@ -5225,11 +5246,8 @@ 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(ss, i, &have_fork_callback) + ss->fork(child); } /** @@ -5273,16 +5291,12 @@ 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(ss, i, &have_exit_callback) { + 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) -- 2.4.2 -- 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/