Andrei Vagin <avagin@xxxxxxxxx> wrote:
> It looks like the c6b3d5bcd67c ("cgroup: fix top cgroup refcnt leak")
> commit was reverted by mistake.
>
> $ mkdir /tmp/cgroup
> $ mkdir /tmp/cgroup2
> $ mount -t cgroup -o none,name=test test /tmp/cgroup
> $ mount -t cgroup -o none,name=test test /tmp/cgroup2
> $ umount /tmp/cgroup
> $ umount /tmp/cgroup2
> $ cat /proc/self/cgroup | grep test
> 12:name=test:/
>
> You can see the test cgroup was not freed.
>
> Cc: Li Zefan <lizefan@xxxxxxxxxx>
> Fixes: aea3f2676c83 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
The kernel (Al's for-next branch, that is) seems to work fine without this
patch; this patch causes the kernel to go bang (trace below).
David
---
percpu ref (css_release) <= 0 (0) after switching to atomic
WARNING: CPU: 1 PID: 0 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x90/0x1a0
Modules linked in:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.20.0-rc1-fscache+ #1256
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x90/0x1a0
Code: d8 48 85 c0 7f 26 80 3d 29 60 ff 00 00 75 1d 48 8b 53 d8 48 c7 c7 00 3c 16 82 c6 05 15 60 ff 00 01 48 8b 73 e8 e8 26 1f ac ff <0f> 0b 48 8d 43 d8 48 89 c7 49 89 c6 ff 53 f0 48 c7 43 f0 00 00 00
RSP: 0018:ffff8800c6c83ed8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8800d3a6e048 RCX: ffff8800c6c83dc4
RDX: 0000000000000003 RSI: ffff8800c5c9cb08 RDI: ffff8800c5c9c340
RBP: ffff8800c6c83ef8 R08: 000000000000003b R09: 0000000000021900
R10: ffff8800c6c83b00 R11: 0000004ac8b230c2 R12: 000060ff39019cd0
R13: ffffffff825b0be8 R14: ffffffffffffffff R15: 0000000000000009
FS: 0000000000000000(0000) GS:ffff8800c6c80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f33b5ad1f54 CR3: 0000000002410001 CR4: 00000000001606e0
Call Trace:
<IRQ>
? rcu_process_callbacks+0x469/0x6de
? percpu_ref_exit+0x26/0x26
rcu_process_callbacks+0x4d7/0x6de
__do_softirq+0x1a5/0x38f
irq_exit+0x63/0xd1
smp_apic_timer_interrupt+0x1cd/0x1e0
apic_timer_interrupt+0xf/0x20
</IRQ>
RIP: 0010:cpuidle_enter_state+0x24e/0x2b1
Code: ff e8 7b be 8a ff 45 84 ed 74 17 9c 58 0f ba e0 09 73 08 0f 0b fa e8 63 8d 94 ff 31 ff e8 14 af 8f ff e8 cd 8b 94 ff fb 85 db <78> 47 48 8b 14 24 b8 ff ff ff 7f 48 b9 ff ff ff ff f3 01 00 00 48
RSP: 0018:ffff8800c5d23ea0 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
RAX: ffff8800c5c9c340 RBX: 0000000000000005 RCX: 000000000000001f
RDX: 0000000000000046 RSI: 0000000000000001 RDI: ffff8800c5c9c340
RBP: 0000000000000005 R08: 0000000000000002 R09: 0000000000021900
R10: 071c71c71c71c71c R11: 0000004ac7f2c3ed R12: ffffe8ffffc89ed0
R13: 0000000000000000 R14: ffffffff8251d478 R15: 0000000000000000
do_idle+0x163/0x1ea
cpu_startup_entry+0x1d/0x1f
start_secondary+0x175/0x190
secondary_startup_64+0xa4/0xb0
irq event stamp: 99625
hardirqs last enabled at (99624): [<ffffffff810b18a5>] vprintk_emit+0xe6/0x24a
hardirqs last disabled at (99625): [<ffffffff81001639>] trace_hardirqs_off_thunk+0x1a/0x1c
softirqs last enabled at (99590): [<ffffffff8105eba9>] irq_enter+0x42/0x5d
softirqs last disabled at (99591): [<ffffffff8105ec27>] irq_exit+0x63/0xd1
---[ end trace f59fd95ebc091779 ]---
