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author | Tejun Heo <tj@kernel.org> | 2013-11-29 10:42:59 -0500 |
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committer | Tejun Heo <tj@kernel.org> | 2013-11-29 10:42:59 -0500 |
commit | 045023658ca1e30dc0bb1f148b42c95b740d3e02 (patch) | |
tree | a97199b0e773e5dd5e420987f96f285644586db2 /kernel/cgroup.c | |
parent | 4bac00d16a8760eae7205e41d2c246477d42a210 (diff) | |
download | op-kernel-dev-045023658ca1e30dc0bb1f148b42c95b740d3e02.zip op-kernel-dev-045023658ca1e30dc0bb1f148b42c95b740d3e02.tar.gz |
cgroup: remove cgroup_pidlist->use_count
After the recent changes, pidlist ref is held only between
cgroup_pidlist_start() and cgroup_pidlist_stop() during which
cgroup->pidlist_mutex is also held. IOW, the reference count is
redundant now. While in use, it's always one and pidlist_mutex is
held - holding the mutex has exactly the same protection.
This patch collapses destroy_dwork queueing into cgroup_pidlist_stop()
so that pidlist_mutex is not released inbetween and drops
pidlist->use_count.
This patch shouldn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r-- | kernel/cgroup.c | 28 |
1 files changed, 7 insertions, 21 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 671cbde..a245803 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3456,8 +3456,6 @@ struct cgroup_pidlist { pid_t *list; /* how many elements the above list has */ int length; - /* how many files are using the current array */ - int use_count; /* each of these stored in a list by its cgroup */ struct list_head links; /* pointer to the cgroup we belong to, for list removal purposes */ @@ -3473,8 +3471,6 @@ struct cgroup_pidlist_open_file { struct cgroup_pidlist *pidlist; }; -static void cgroup_release_pid_array(struct cgroup_pidlist *l); - /* * The following two functions "fix" the issue where there are more pids * than kmalloc will give memory for; in such cases, we use vmalloc/vfree. @@ -3524,10 +3520,10 @@ static void cgroup_pidlist_destroy_work_fn(struct work_struct *work) mutex_lock(&l->owner->pidlist_mutex); /* - * Destroy iff we didn't race with a new user or get queued again. - * Queued state won't change as it can only be queued while locked. + * Destroy iff we didn't get queued again. The state won't change + * as destroy_dwork can only be queued while locked. */ - if (!l->use_count && !delayed_work_pending(dwork)) { + if (!delayed_work_pending(dwork)) { list_del(&l->links); pidlist_free(l->list); put_pid_ns(l->key.ns); @@ -3775,7 +3771,6 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos) return ERR_PTR(ret); } l = of->pidlist; - l->use_count++; if (pid) { int end = l->length; @@ -3804,9 +3799,11 @@ static void cgroup_pidlist_stop(struct seq_file *s, void *v) { struct cgroup_pidlist_open_file *of = s->private; - mutex_unlock(&of->cgrp->pidlist_mutex); if (of->pidlist) - cgroup_release_pid_array(of->pidlist); + mod_delayed_work(cgroup_pidlist_destroy_wq, + &of->pidlist->destroy_dwork, + CGROUP_PIDLIST_DESTROY_DELAY); + mutex_unlock(&of->cgrp->pidlist_mutex); } static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos) @@ -3844,17 +3841,6 @@ static const struct seq_operations cgroup_pidlist_seq_operations = { .show = cgroup_pidlist_show, }; -static void cgroup_release_pid_array(struct cgroup_pidlist *l) -{ - mutex_lock(&l->owner->pidlist_mutex); - BUG_ON(!l->use_count); - /* if the last user, arm the destroy work */ - if (!--l->use_count) - mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, - CGROUP_PIDLIST_DESTROY_DELAY); - mutex_unlock(&l->owner->pidlist_mutex); -} - static const struct file_operations cgroup_pidlist_operations = { .read = seq_read, .llseek = seq_lseek, |