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146aa1bd05
put_css_set_taskexit may be called when find_css_set is called on other
cpu. And the race will occur:
put_css_set_taskexit side find_css_set side
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atomic_dec_and_test(&kref->refcount) |
/* kref->refcount = 0 */ |
....................................................................
| read_lock(&css_set_lock)
| find_existing_css_set
| get_css_set
| read_unlock(&css_set_lock);
....................................................................
__release_css_set |
....................................................................
| /* use a released css_set */
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[put_css_set is the same. But in the current code, all put_css_set are
put into cgroup mutex critical region as the same as find_css_set.]
[akpm@linux-foundation.org: repair comments]
[menage@google.com: eliminate race in css_set refcounting]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
107 lines
2 KiB
C
107 lines
2 KiB
C
/*
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* kernel/cgroup_debug.c - Example cgroup subsystem that
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* exposes debug info
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*
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* Copyright (C) Google Inc, 2007
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*
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* Developed by Paul Menage (menage@google.com)
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*
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*/
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#include <linux/cgroup.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/rcupdate.h>
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#include <asm/atomic.h>
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static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
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struct cgroup *cont)
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{
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struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
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if (!css)
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return ERR_PTR(-ENOMEM);
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return css;
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}
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static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
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{
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kfree(cont->subsys[debug_subsys_id]);
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}
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static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
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{
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return atomic_read(&cont->count);
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}
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static u64 taskcount_read(struct cgroup *cont, struct cftype *cft)
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{
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u64 count;
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cgroup_lock();
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count = cgroup_task_count(cont);
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cgroup_unlock();
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return count;
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}
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static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
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{
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return (u64)(long)current->cgroups;
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}
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static u64 current_css_set_refcount_read(struct cgroup *cont,
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struct cftype *cft)
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{
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u64 count;
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rcu_read_lock();
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count = atomic_read(¤t->cgroups->refcount);
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rcu_read_unlock();
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return count;
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}
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static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
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{
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return test_bit(CGRP_RELEASABLE, &cgrp->flags);
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}
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static struct cftype files[] = {
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{
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.name = "cgroup_refcount",
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.read_u64 = cgroup_refcount_read,
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},
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{
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.name = "taskcount",
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.read_u64 = taskcount_read,
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},
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{
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.name = "current_css_set",
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.read_u64 = current_css_set_read,
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},
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{
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.name = "current_css_set_refcount",
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.read_u64 = current_css_set_refcount_read,
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},
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{
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.name = "releasable",
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.read_u64 = releasable_read,
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},
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};
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static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
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{
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return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
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}
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struct cgroup_subsys debug_subsys = {
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.name = "debug",
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.create = debug_create,
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.destroy = debug_destroy,
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.populate = debug_populate,
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.subsys_id = debug_subsys_id,
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};
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