The patch titled
cgroups: fix race between userspace and kernelspace
has been added to the -mm tree. Its filename is
cgroups-fix-race-between-userspace-and-kernelspace.patch
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: cgroups: fix race between userspace and kernelspace
From: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Notify userspace about cgroup removing only after rmdir of cgroup
directory to avoid race between userspace and kernelspace.
Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Dan Malek <dan@xxxxxxxxxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)
diff -puN kernel/cgroup.c~cgroups-fix-race-between-userspace-and-kernelspace kernel/cgroup.c
--- a/kernel/cgroup.c~cgroups-fix-race-between-userspace-and-kernelspace
+++ a/kernel/cgroup.c
@@ -780,28 +780,15 @@ static struct inode *cgroup_new_inode(mo
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
- struct cgroup_event *event, *tmp;
int ret = 0;
for_each_subsys(cgrp->root, ss)
if (ss->pre_destroy) {
ret = ss->pre_destroy(ss, cgrp);
if (ret)
- goto out;
+ break;
}
- /*
- * Unregister events and notify userspace.
- */
- spin_lock(&cgrp->event_list_lock);
- list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
- list_del(&event->list);
- eventfd_signal(event->eventfd, 1);
- schedule_work(&event->remove);
- }
- spin_unlock(&cgrp->event_list_lock);
-
-out:
return ret;
}
@@ -2991,7 +2978,6 @@ static void cgroup_event_remove(struct w
event->cft->unregister_event(cgrp, event->cft, event->eventfd);
eventfd_ctx_put(event->eventfd);
- remove_wait_queue(event->wqh, &event->wait);
kfree(event);
}
@@ -3009,6 +2995,7 @@ static int cgroup_event_wake(wait_queue_
unsigned long flags = (unsigned long)key;
if (flags & POLLHUP) {
+ remove_wait_queue_locked(event->wqh, &event->wait);
spin_lock(&cgrp->event_list_lock);
list_del(&event->list);
spin_unlock(&cgrp->event_list_lock);
@@ -3457,6 +3444,7 @@ static int cgroup_rmdir(struct inode *un
struct dentry *d;
struct cgroup *parent;
DEFINE_WAIT(wait);
+ struct cgroup_event *event, *tmp;
int ret;
/* the vfs holds both inode->i_mutex already */
@@ -3540,6 +3528,20 @@ again:
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
+ /*
+ * Unregister events and notify userspace.
+ * Notify userspace about cgroup removing only after rmdir of cgroup
+ * directory to avoid race between userspace and kernelspace
+ */
+ spin_lock(&cgrp->event_list_lock);
+ list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
+ list_del(&event->list);
+ remove_wait_queue(event->wqh, &event->wait);
+ eventfd_signal(event->eventfd, 1);
+ schedule_work(&event->remove);
+ }
+ spin_unlock(&cgrp->event_list_lock);
+
mutex_unlock(&cgroup_mutex);
return 0;
}
_
Patches currently in -mm which might be from kirill@xxxxxxxxxxxxx are
cgroups-fix-contents-in-cgroups-documentation.patch
cgroup-implement-eventfd-based-generic-api-for-notifications.patch
cgroup-implement-eventfd-based-generic-api-for-notifications-kconfig-fix.patch
cgroup-implement-eventfd-based-generic-api-for-notifications-fixes.patch
memcg-extract-mem_group_usage-from-mem_cgroup_read.patch
memcg-rework-usage-of-stats-by-soft-limit.patch
memcg-implement-memory-thresholds.patch
memcg-implement-memory-thresholds-checkpatch-fixes.patch
memcg-implement-memory-thresholds-checkpatch-fixes-fix.patch
memcg-implement-memory-thresholds-check-if-first-threshold-crossed.patch
memcg-typo-in-comment-to-mem_cgroup_print_oom_info.patch
memcg-update-threshold-and-softlimit-at-commit-v2.patch
memcg-share-event-counter-rather-than-duplicate-v2.patch
memcg-update-memcg_testtxt.patch
cgroups-fix-race-between-userspace-and-kernelspace.patch
cgroups-remove-events-before-destroying-subsystem-state-objects.patch
cgroups-add-simple-listener-of-cgroup-events-to-documentation.patch
memcg-update-memcg_testtxt-to-describe-memory-thresholds.patch
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