[no subject]

From: Tejun Heo
Date: Tue Jun 18 2013 - 14:14:22 EST

cgroup_serial_nr_cursor was created atomic64_t because I thought it
was never gonna used for anything other than assigning unique numbers
to cgroups and didn't want to worry about synchronization; however,
now we're using it as an event-stamp to distinguish cgroups created
before and after certain point which assumes that it's protected by

Let's make it clear by making it a u64. Also, rename it to
cgroup_serial_nr_next and make it point to the next nr to allocate so
that where it's pointing to is clear and more conventional.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Applied to cgroup/for-3.11 as a follow-up.


kernel/cgroup.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0ed7d8d..65f333e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -203,9 +203,10 @@ static struct cgroup_name root_cgroup_name = { .name = "/" };
* guarantees cgroups with bigger numbers are newer than those with smaller
* numbers. Also, as cgroups are always appended to the parent's
* ->children list, it guarantees that sibling cgroups are always sorted in
- * the ascending serial number order on the list.
+ * the ascending serial number order on the list. Protected by
+ * cgroup_mutex.
-static atomic64_t cgroup_serial_nr_cursor = ATOMIC64_INIT(0);
+static u64 cgroup_serial_nr_next = 1;

/* This flag indicates whether tasks in the fork and exit paths should
* check for fork/exit handlers to call. This avoids us having to do
@@ -2803,7 +2804,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,
struct super_block *sb = ss->root->sb;
struct dentry *prev = NULL;
struct inode *inode;
- u64 update_upto;
+ u64 update_before;

/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
if (!cfts || ss->root == &rootnode ||
@@ -2815,9 +2816,9 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,
* All cgroups which are created after we drop cgroup_mutex will
* have the updated set of files, so we only need to update the
- * cgroups created before the current @cgroup_serial_nr_cursor.
+ * cgroups created before the current @cgroup_serial_nr_next.
- update_upto = atomic64_read(&cgroup_serial_nr_cursor);
+ update_before = cgroup_serial_nr_next;


@@ -2844,7 +2845,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,

- if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp))
+ if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))
cgroup_addrm_files(cgrp, ss, cfts, is_add);
@@ -4327,7 +4328,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
goto err_free_all;

- cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor);
+ cgrp->serial_nr = cgroup_serial_nr_next++;

/* allocation complete, commit to creation */
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);

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