[Devel] Re: [PATCH 13/28] [PREP 13/14] Miscellaneous preparations in pid namespaces

[Pavel Emelianov]

sukadev at us.ibm.com wrote:
> Pavel Emelianov [xemul at openvz.org] wrote:
> | The most important one is moving exit_task_namespaces behind exit_notify
> | in do_exit() to make it possible to see the task's pid namespace to
> | properly notify the parent.
> 
> Hmm. I think we tried this once a few months ago and got a crash in nfsd
> See http://lkml.org/lkml/2007/1/17/75
> 
>             [<c01f6115>] lockd_down+0x125/0x190
>             [<c01d26bd>] nfs_free_server+0x6d/0xd0
>             [<c01d8e9c>] nfs_kill_super+0xc/0x20
>             [<c0161c5d>] deactivate_super+0x7d/0xa0
>             [<c0175e0e>] release_mounts+0x6e/0x80
>             [<c0175e86>] __put_mnt_ns+0x66/0x80
>             [<c0132b3e>] free_nsproxy+0x5e/0x60
>                 // exit_task_namespaces() after returning from exit_notify()
>             [<c011f021>] do_exit+0x791/0x810
>             [<c011f0c6>] do_group_exit+0x26/0x70
>             [<c0103142>] sysenter_past_esp+0x5f/0x85
> 
> exit_notify() sets current->sighand to NULL and I think lockd_down() called
> from exit_task_namespaces/__put_mnt_ns() was accesssing current->sighand.

If sighand is set to NULL and then accessed then how is this related to pid namespace? 

> Do your other patches in this set tweak something to prevent it ?

I think no. I'll check it for my current patches.

> Thats one of the reasons we had to remove pid_ns from nsproxy and use
> the pid_ns from pid->upid_list[i]->pid_ns.
> 
> Suka
> 

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