diff options
| author | Tejun Heo <tj@kernel.org> | 2014-02-11 11:52:47 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-02-11 11:52:47 -0500 |
| commit | 4ac0601744eb86e982fbdadde35f1945f7ce5882 (patch) | |
| tree | 887f0cbc2853802ad113b87f0d2c5b764e2619ce | |
| parent | ace2bee8135a3dc725958b8d08c55ee9df813d39 (diff) | |
cgroup: release cgroup_mutex over file removals
Now that cftypes and all tree modification operations are protected by
cgroup_tree_mutex, we can drop cgroup_mutex while deleting files and
directories. Drop cgroup_mutex over removals.
This doesn't make any noticeable difference now but is to help kernfs
conversion. In kernfs, removals are sync points which drain in-flight
operations as those operations would grab cgroup_mutex, trying to
delete under cgroup_mutex would deadlock. This can be resolved by
just holding the outer cgroup_tree_mutex which nests outside both
kernfs active reference and cgroup_mutex.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
| -rw-r--r-- | kernel/cgroup.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index cb20d12cb09..d28cf75f33c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -976,7 +976,9 @@ static int rebind_subsystems(struct cgroupfs_root *root, * Nothing can fail from this point on. Remove files for the * removed subsystems and rebind each subsystem. */ + mutex_unlock(&cgroup_mutex); cgroup_clear_dir(cgrp, removed_mask); + mutex_lock(&cgroup_mutex); for_each_subsys(ss, i) { unsigned long bit = 1UL << i; @@ -2696,10 +2698,11 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) u64 update_before; int ret = 0; + mutex_unlock(&cgroup_mutex); + /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ if (!cfts || ss->root == &cgroup_dummy_root || !atomic_inc_not_zero(&sb->s_active)) { - mutex_unlock(&cgroup_mutex); mutex_unlock(&cgroup_tree_mutex); return 0; } @@ -2723,18 +2726,15 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) dput(prev); prev = cgrp->dentry; - mutex_unlock(&cgroup_mutex); mutex_unlock(&cgroup_tree_mutex); mutex_lock(&inode->i_mutex); mutex_lock(&cgroup_tree_mutex); - mutex_lock(&cgroup_mutex); if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp)) ret = cgroup_addrm_files(cgrp, cfts, is_add); mutex_unlock(&inode->i_mutex); if (ret) break; } - mutex_unlock(&cgroup_mutex); mutex_unlock(&cgroup_tree_mutex); dput(prev); deactivate_super(sb); @@ -4387,10 +4387,13 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) /* * Initiate massacre of all css's. cgroup_destroy_css_killed() * will be invoked to perform the rest of destruction once the - * percpu refs of all css's are confirmed to be killed. + * percpu refs of all css's are confirmed to be killed. This + * involves removing the subsystem's files, drop cgroup_mutex. */ + mutex_unlock(&cgroup_mutex); for_each_css(css, ssid, cgrp) kill_css(css); + mutex_lock(&cgroup_mutex); /* * Mark @cgrp dead. This prevents further task migration and child @@ -4421,9 +4424,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) * puts the base ref but we aren't quite done with @cgrp yet, so * hold onto it. */ + mutex_unlock(&cgroup_mutex); cgroup_addrm_files(cgrp, cgroup_base_files, false); dget(d); cgroup_d_remove_dir(d); + mutex_lock(&cgroup_mutex); return 0; }; |