From: Tejun Heo <tj@kernel.org>
To: lizefan@huawei.com, hannes@cmpxchg.org
Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, Tejun Heo <tj@kernel.org>
Subject: [PATCH 06/12] cgroup: factor out cgroup_drain_offline() from cgroup_subtree_control_write()
Date: Mon, 22 Feb 2016 22:45:40 -0500 [thread overview]
Message-ID: <1456199146-14765-7-git-send-email-tj@kernel.org> (raw)
In-Reply-To: <1456199146-14765-1-git-send-email-tj@kernel.org>
Factor out async css offline draining into cgroup_drain_offline().
* Nest subsystem walk inside child walk. The child walk will later be
converted to subtree walk which is a bit more expensive.
* Relocate the draining above subsystem mask preparation, which
doesn't create any behavior differences but helps further
refactoring.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 77 ++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 52 insertions(+), 25 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0282797..7966750 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2960,6 +2960,53 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
return ret;
}
+/**
+ * cgroup_drain_offline - wait for previously offlined csses to go away
+ * @cgrp: parent of the target cgroups
+ *
+ * Because css offlining is asynchronous, userland may try to re-enable a
+ * controller while the previous css is still around. This function drains
+ * the previous css instances of @cgrp's children.
+ *
+ * Must be called with cgroup_mutex held. Returns %false if there were no
+ * dying css instances. Returns %true if there were one or more and this
+ * function waited. On %true return, cgroup_mutex has been dropped and
+ * re-acquired inbetween which anything could have happened. The caller
+ * typically would have to start over.
+ */
+static bool cgroup_drain_offline(struct cgroup *cgrp)
+{
+ struct cgroup *dsct;
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ cgroup_for_each_live_child(dsct, cgrp) {
+ for_each_subsys(ss, ssid) {
+ struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
+ DEFINE_WAIT(wait);
+
+ if (!css)
+ continue;
+
+ cgroup_get(dsct);
+ prepare_to_wait(&dsct->offline_waitq, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ mutex_unlock(&cgroup_mutex);
+ schedule();
+ finish_wait(&dsct->offline_waitq, &wait);
+ mutex_lock(&cgroup_mutex);
+
+ cgroup_put(dsct);
+ return true;
+ }
+ }
+
+ return false;
+}
+
/* change the enabled child controllers for a cgroup in the default hierarchy */
static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
@@ -3048,6 +3095,11 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
goto out_unlock;
}
+ if (cgroup_drain_offline(cgrp)) {
+ cgroup_kn_unlock(of->kn);
+ return restart_syscall();
+ }
+
/*
* Update subsys masks and calculate what needs to be done. More
* subsystems than specified may need to be enabled or disabled
@@ -3063,31 +3115,6 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
enable |= css_enable;
disable |= css_disable;
- /*
- * Because css offlining is asynchronous, userland might try to
- * re-enable the same controller while the previous instance is
- * still around. In such cases, wait till it's gone using
- * offline_waitq.
- */
- do_each_subsys_mask(ss, ssid, css_enable) {
- cgroup_for_each_live_child(child, cgrp) {
- DEFINE_WAIT(wait);
-
- if (!cgroup_css(child, ss))
- continue;
-
- cgroup_get(child);
- prepare_to_wait(&child->offline_waitq, &wait,
- TASK_UNINTERRUPTIBLE);
- cgroup_kn_unlock(of->kn);
- schedule();
- finish_wait(&child->offline_waitq, &wait);
- cgroup_put(child);
-
- return restart_syscall();
- }
- } while_each_subsys_mask();
-
cgrp->subtree_control = new_sc;
cgrp->subtree_ss_mask = new_ss;
--
2.5.0
next prev parent reply other threads:[~2016-02-23 3:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 3:45 [PATCHSET cgroup/for-4.6] cgroup: make control mask updates modular and recursive Tejun Heo
2016-02-23 3:45 ` [PATCH 01/12] cgroup: separate out interface file creation from css creation Tejun Heo
2016-02-23 3:45 ` [PATCH 02/12] cgroup: explicitly track whether a cgroup_subsys_state is visible to userland Tejun Heo
2016-02-23 3:45 ` [PATCH 03/12] cgroup: reorder operations in cgroup_mkdir() Tejun Heo
2016-02-23 3:45 ` [PATCH 04/12] cgroup: factor out cgroup_create() out of cgroup_mkdir() Tejun Heo
2016-02-23 3:45 ` [PATCH 05/12] cgroup: introduce cgroup_control() and cgroup_ss_mask() Tejun Heo
2016-02-23 3:45 ` Tejun Heo [this message]
2016-02-23 3:45 ` [PATCH 07/12] cgroup: factor out cgroup_apply_control_disable() from cgroup_subtree_control_write() Tejun Heo
2016-02-23 3:45 ` [PATCH 08/12] cgroup: factor out cgroup_apply_control_enable() " Tejun Heo
2016-02-23 3:45 ` [PATCH 09/12] cgroup: make cgroup_drain_offline() and cgroup_apply_control_{disable|enable}() recursive Tejun Heo
2016-02-23 3:45 ` [PATCH 10/12] cgroup: introduce cgroup_{save|propagate|restore}_control() Tejun Heo
2016-02-23 3:45 ` [PATCH 11/12] cgroup: Factor out cgroup_{apply|finalize}_control() from cgroup_subtree_control_write() Tejun Heo
2016-02-23 3:45 ` [PATCH 12/12] cgroup: make cgroup_calc_subtree_ss_mask() take @this_ss_mask Tejun Heo
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