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authorLai Jiangshan <laijs@cn.fujitsu.com>2009-01-07 18:07:37 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-08 08:31:02 -0800
commitb2aa30f7bb381e04c93eed106089ba55553955f1 (patch)
treeeda632102a0bc6e325a24e77a9c2819eab5aeef3
parent2019f634ce5904c19eba4e86f51b1a119a53a9f1 (diff)
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cgroups: don't put struct cgroupfs_root protected by RCU
We don't access struct cgroupfs_root in fast path, so we should not put struct cgroupfs_root protected by RCU But the comment in struct cgroup_subsys.root confuse us. struct cgroup_subsys.root is used in these places: 1 find_css_set(): if (ss->root->subsys_list.next == &ss->sibling) 2 rebind_subsystems(): if (ss->root != &rootnode) rcu_assign_pointer(ss->root, root); rcu_assign_pointer(subsys[i]->root, &rootnode); 3 cgroup_has_css_refs(): if (ss->root != cgrp->root) 4 cgroup_init_subsys(): ss->root = &rootnode; 5 proc_cgroupstats_show(): ss->name, ss->root->subsys_bits, ss->root->number_of_cgroups, !ss->disabled); 6 cgroup_clone(): root = subsys->root; if ((root != subsys->root) || All these place we have held cgroup_lock() or we don't dereference to struct cgroupfs_root. It's means wo don't need RCU when use struct cgroup_subsys.root, and we should not put struct cgroupfs_root protected by RCU. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Reviewed-by: Paul Menage <menage@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/cgroup.h1
-rw-r--r--kernel/cgroup.c4
2 files changed, 2 insertions, 3 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 08b78c09b09a..f68dfd8dd53a 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -337,7 +337,6 @@ struct cgroup_subsys {
#define MAX_CGROUP_TYPE_NAMELEN 32
const char *name;
- /* Protected by RCU */
struct cgroupfs_root *root;
struct list_head sibling;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a391ab3bdfc6..a288da176e46 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -713,7 +713,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
cgrp->subsys[i] = dummytop->subsys[i];
cgrp->subsys[i]->cgroup = cgrp;
list_add(&ss->sibling, &root->subsys_list);
- rcu_assign_pointer(ss->root, root);
+ ss->root = root;
if (ss->bind)
ss->bind(ss, cgrp);
@@ -725,7 +725,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
ss->bind(ss, dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cgrp->subsys[i] = NULL;
- rcu_assign_pointer(subsys[i]->root, &rootnode);
+ subsys[i]->root = &rootnode;
list_del(&ss->sibling);
} else if (bit & final_bits) {
/* Subsystem state should already exist */