2023-05-17 08:11:08

by Muchun Song

Subject: Re: [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer_tasks()

> On May 17, 2023, at 15:45, Qi Zheng <[email protected]> wrote:
>
> From: Qi Zheng <[email protected]>
>
> The commit 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock()
> deadlock") fixed the deadlock between cgroup_threadgroup_rwsem and
> cpus_read_lock() by introducing cgroup_attach_{lock,unlock}() and removing
> cpus_read_{lock,unlock}() from cpuset_attach(). But cgroup_transfer_tasks()
> was missed and not handled, which will cause th following warning:
>
> WARNING: CPU: 0 PID: 589 at kernel/cpu.c:526 lockdep_assert_cpus_held+0x32/0x40
> CPU: 0 PID: 589 Comm: kworker/1:4 Not tainted 6.4.0-rc2-next-20230517 #50
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
> Workqueue: events cpuset_hotplug_workfn
> RIP: 0010:lockdep_assert_cpus_held+0x32/0x40
> <...>
> Call Trace:
> <TASK>
> cpuset_attach+0x40/0x240
> cgroup_migrate_execute+0x452/0x5e0
> ? _raw_spin_unlock_irq+0x28/0x40
> cgroup_transfer_tasks+0x1f3/0x360
> ? find_held_lock+0x32/0x90
> ? cpuset_hotplug_workfn+0xc81/0xed0
> cpuset_hotplug_workfn+0xcb1/0xed0
> ? process_one_work+0x248/0x5b0
> process_one_work+0x2b9/0x5b0
> worker_thread+0x56/0x3b0
> ? process_one_work+0x5b0/0x5b0
> kthread+0xf1/0x120
> ? kthread_complete_and_exit+0x20/0x20
> ret_from_fork+0x1f/0x30
> </TASK>
>
> So just use the cgroup_attach_{lock,unlock}() helper to fix it.
>
> Fixes: 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
> Reported-by: Zhao Gongyi <[email protected]>
> Signed-off-by: Qi Zheng <[email protected]>

Acked-by: Muchun Song <[email protected]>

Thanks.

2023-05-22 03:13:13

by Qi Zheng

Subject: Re: [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer_tasks()

On 2023/5/17 15:51, Muchun Song wrote:
>
>
>> On May 17, 2023, at 15:45, Qi Zheng <[email protected]> wrote:
>>
>> From: Qi Zheng <[email protected]>
>>
>> The commit 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock()
>> deadlock") fixed the deadlock between cgroup_threadgroup_rwsem and
>> cpus_read_lock() by introducing cgroup_attach_{lock,unlock}() and removing
>> cpus_read_{lock,unlock}() from cpuset_attach(). But cgroup_transfer_tasks()
>> was missed and not handled, which will cause th following warning:
>>
>> WARNING: CPU: 0 PID: 589 at kernel/cpu.c:526 lockdep_assert_cpus_held+0x32/0x40
>> CPU: 0 PID: 589 Comm: kworker/1:4 Not tainted 6.4.0-rc2-next-20230517 #50
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
>> Workqueue: events cpuset_hotplug_workfn
>> RIP: 0010:lockdep_assert_cpus_held+0x32/0x40
>> <...>
>> Call Trace:
>> <TASK>
>> cpuset_attach+0x40/0x240
>> cgroup_migrate_execute+0x452/0x5e0
>> ? _raw_spin_unlock_irq+0x28/0x40
>> cgroup_transfer_tasks+0x1f3/0x360
>> ? find_held_lock+0x32/0x90
>> ? cpuset_hotplug_workfn+0xc81/0xed0
>> cpuset_hotplug_workfn+0xcb1/0xed0
>> ? process_one_work+0x248/0x5b0
>> process_one_work+0x2b9/0x5b0
>> worker_thread+0x56/0x3b0
>> ? process_one_work+0x5b0/0x5b0
>> kthread+0xf1/0x120
>> ? kthread_complete_and_exit+0x20/0x20
>> ret_from_fork+0x1f/0x30
>> </TASK>
>>
>> So just use the cgroup_attach_{lock,unlock}() helper to fix it.
>>
>> Fixes: 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
>> Reported-by: Zhao Gongyi <[email protected]>
>> Signed-off-by: Qi Zheng <[email protected]>
>
> Acked-by: Muchun Song <[email protected]>

Thanks. And hi Tejun, Can this patch be applied?

>
> Thanks.
>

--
Thanks,
Qi