* [RFC PATCH next]cgroup: use css_get() in cgroup_create() to check CSS_ROOT
@ 2013-08-16 9:57 Li Zhong
2013-08-16 10:16 ` Li Zefan
0 siblings, 1 reply; 3+ messages in thread
From: Li Zhong @ 2013-08-16 9:57 UTC (permalink / raw)
To: linux-next list; +Cc: Tejun Heo, Li Zefan
It seems that the root css doesn't have refcnt allocated(not needed?),
and would cause the booting error attached.
This patch tries to use css_get() to not increase the refcnt if parent
is root.
[ 0.792038] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 0.792937] IP: [<ffffffff810b37cc>] cgroup_mkdir+0x37c/0x740
[ 0.793027] PGD 0
[ 0.793027] Oops: 0002 [#1]
[ 0.793027] Modules linked in:
[ 0.793027] CPU: 0 PID: 1 Comm: systemd Not tainted 3.11.0-rc5-next-20130815+ #1
[ 0.793027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[ 0.793027] task: ffff88007f868000 ti: ffff88007f864000 task.ti: ffff88007f864000
[ 0.793027] RIP: 0010:[<ffffffff810b37cc>] [<ffffffff810b37cc>] cgroup_mkdir+0x37c/0x740
[ 0.793027] RSP: 0018:ffff88007f865df8 EFLAGS: 00010246
[ 0.793027] RAX: 0000000000000000 RBX: ffffffff81a46ee0 RCX: 0000000000000001
[ 0.793027] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff81a415c0
[ 0.793027] RBP: ffff88007f865ec8 R08: 0000000000000001 R09: 0000000000000000
[ 0.793027] R10: ffff88007ce6d060 R11: 0000000000000000 R12: ffff88007ce6d000
[ 0.793027] R13: ffff88007ce6d060 R14: ffffffff81a46d80 R15: ffff88007c6e8018
[ 0.793027] FS: 00007f13dbf6f840(0000) GS:ffffffff81a23000(0000) knlGS:0000000000000000
[ 0.793027] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.793027] CR2: 0000000000000000 CR3: 000000007b7e5000 CR4: 00000000000006b0
[ 0.793027] Stack:
[ 0.793027] ffffffff810b380d 0000000000000002 ffff88007f865e18 ffffffff81167069
[ 0.793027] ffff88007f865ed8 ffffffff8116a3f5 ffff880037454400 ffff88007c6e8018
[ 0.793027] ffff88007c6e8028 ffff88007c6e8328 ffff88007c6e8000 ffff88007ce6d000
[ 0.793027] Call Trace:
[ 0.793027] [<ffffffff810b380d>] ? cgroup_mkdir+0x3bd/0x740
[ 0.793027] [<ffffffff81167069>] ? lookup_hash+0x19/0x20
[ 0.793027] [<ffffffff8116a3f5>] ? kern_path_create+0x95/0x170
[ 0.793027] [<ffffffff8116ce3e>] vfs_mkdir+0x9e/0xf0
[ 0.793027] [<ffffffff8116d7a0>] SyS_mkdirat+0x60/0xe0
[ 0.793027] [<ffffffff8116d839>] SyS_mkdir+0x19/0x20
[ 0.793027] [<ffffffff814c960d>] tracesys+0xcf/0xd4
[ 0.793027] Code: ad 70 ff ff ff 48 89 9d 60 ff ff ff 4d 89 d5 4c 8b bd 68 ff ff ff 4c 8b 65 88 eb 50 0f 1f 00 48 8b 43 18 a8 03 0f 85 6c 03 00 00 <ff> 00 e8 1d 0a fb ff 85 c0 74 0d 80 3d f0 45 a1 00 00 0f 84 4c
[ 0.793027] RIP [<ffffffff810b37cc>] cgroup_mkdir+0x37c/0x740
[ 0.793027] RSP <ffff88007f865df8>
[ 0.793027] CR2: 0000000000000000
[ 0.827296] ---[ end trace a4b14b49bc46fd60 ]---
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
kernel/cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 723194f..781f8cd 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4485,7 +4485,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
dget(dentry);
- percpu_ref_get(&css->parent->refcnt);
+ css_get(css->parent);
}
/* hold a ref to the parent's dentry */
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH next]cgroup: use css_get() in cgroup_create() to check CSS_ROOT
2013-08-16 9:57 [RFC PATCH next]cgroup: use css_get() in cgroup_create() to check CSS_ROOT Li Zhong
@ 2013-08-16 10:16 ` Li Zefan
2013-08-16 14:58 ` Tejun Heo
0 siblings, 1 reply; 3+ messages in thread
From: Li Zefan @ 2013-08-16 10:16 UTC (permalink / raw)
To: Li Zhong; +Cc: linux-next list, Tejun Heo
On 2013/8/16 17:57, Li Zhong wrote:
> It seems that the root css doesn't have refcnt allocated(not needed?),
> and would cause the booting error attached.
>
> This patch tries to use css_get() to not increase the refcnt if parent
> is root.
...
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 723194f..781f8cd 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -4485,7 +4485,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
>
> dget(dentry);
> - percpu_ref_get(&css->parent->refcnt);
> + css_get(css->parent);
We use css_put() to drop this refcnt, so it makes sense to use css_get()
for consistency.
Acked-by: Li Zefan <lizefan@huawei.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC PATCH next]cgroup: use css_get() in cgroup_create() to check CSS_ROOT
2013-08-16 10:16 ` Li Zefan
@ 2013-08-16 14:58 ` Tejun Heo
0 siblings, 0 replies; 3+ messages in thread
From: Tejun Heo @ 2013-08-16 14:58 UTC (permalink / raw)
To: Li Zefan; +Cc: Li Zhong, linux-next list
On Fri, Aug 16, 2013 at 06:16:18PM +0800, Li Zefan wrote:
> On 2013/8/16 17:57, Li Zhong wrote:
> > It seems that the root css doesn't have refcnt allocated(not needed?),
> > and would cause the booting error attached.
> >
> > This patch tries to use css_get() to not increase the refcnt if parent
> > is root.
> ...
> > diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> > index 723194f..781f8cd 100644
> > --- a/kernel/cgroup.c
> > +++ b/kernel/cgroup.c
> > @@ -4485,7 +4485,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> > struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
> >
> > dget(dentry);
> > - percpu_ref_get(&css->parent->refcnt);
> > + css_get(css->parent);
>
> We use css_put() to drop this refcnt, so it makes sense to use css_get()
> for consistency.
>
> Acked-by: Li Zefan <lizefan@huawei.com>
Heh, this doesn't trigger on my test setup for some reason. Applied.
Thanks a lot.
--
tejun
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-08-16 14:58 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-08-16 9:57 [RFC PATCH next]cgroup: use css_get() in cgroup_create() to check CSS_ROOT Li Zhong
2013-08-16 10:16 ` Li Zefan
2013-08-16 14:58 ` Tejun Heo
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).