Home » Mailing lists » Devel » [PATCH 0/3] Fix problem with static_key decrement
| [PATCH 2/3] don't take cgroup_mutex in destroy() [message #45944 is a reply to message #45943] |
Thu, 19 April 2012 22:49   |
Glauber Costa
Messages: 916
Registered: October 2011
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Senior Member |
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Most of the destroy functions are only doing very simple things
like freeing memory.
The ones who goes through lists and such, already use its own
locking for those.
* The cgroup itself won't go away until we free it, (after destroy)
* The parent won't go away because we hold a reference count
* There are no more tasks in the cgroup, and the cgroup is declared
dead (cgroup_is_removed() == true)
For the blk-cgroup and the cpusets, I got the impression that the mutex
is still necessary.
For those, I grabbed it from within the destroy function itself.
If the maintainer for those subsystems consider it safe to remove
it, we can discuss it separately.
Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Tejun Heo <tj@kernel.org>
CC: Li Zefan <lizefan@huawei.com>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 2 ++
kernel/cgroup.c | 9 ++++-----
kernel/cpuset.c | 2 ++
3 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 126c341..477463f 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1527,6 +1527,7 @@ static void blkiocg_destroy(struct cgroup *cgroup)
struct blkio_policy_type *blkiop;
struct blkio_policy_node *pn, *pntmp;
+ cgroup_lock();
rcu_read_lock();
do {
spin_lock_irqsave(&blkcg->lock, flags);
@@ -1566,6 +1567,7 @@ static void blkiocg_destroy(struct cgroup *cgroup)
rcu_read_unlock();
if (blkcg != &blkio_root_cgroup)
kfree(blkcg);
+ cgroup_unlock();
}
static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 932c318..976d332 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -869,13 +869,13 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
* agent */
synchronize_rcu();
- mutex_lock(&cgroup_mutex);
/*
* Release the subsystem state objects.
*/
for_each_subsys(cgrp->root, ss)
ss->destroy(cgrp);
+ mutex_lock(&cgroup_mutex);
cgrp->root->number_of_cgroups--;
mutex_unlock(&cgroup_mutex);
@@ -3994,13 +3994,12 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
err_destroy:
+ mutex_unlock(&cgroup_mutex);
for_each_subsys(root, ss) {
if (cgrp->subsys[ss->subsys_id])
ss->destroy(cgrp);
}
- mutex_unlock(&cgroup_mutex);
-
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
@@ -4349,9 +4348,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
int ret = cgroup_init_idr(ss, css);
if (ret) {
dummytop->subsys[ss->subsys_id] = NULL;
+ mutex_unlock(&cgroup_mutex);
ss->destroy(dummytop);
subsys[i] = NULL;
- mutex_unlock(&cgroup_mutex);
return ret;
}
}
@@ -4447,10 +4446,10 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
* pointer to find their state. note that this also takes care of
* freeing the css_id.
*/
+ mutex_unlock(&cgroup_mutex);
ss->destroy(dummytop);
dummytop->subsys[ss->subsys_id] = NULL;
- mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 8c8bd65..3cd4916 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1862,10 +1862,12 @@ static void cpuset_destroy(struct cgroup *cont)
{
struct cpuset *cs = cgroup_cs(cont);
+ cgroup_lock();
if (is_sched_load_balance(cs))
update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
number_of_cpusets--;
+ cgroup_unlock();
free_cpumask_var(cs->cpus_allowed);
kfree(cs);
}
--
1.7.7.6
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