Re: [PATCH] move exit_task_work() before exit_fs().

From: Peter Hurley
Date: Sun Dec 28 2014 - 20:09:51 EST

On 12/28/2014 07:58 PM, Ma, Xindong wrote:
>> On 12/26, Leon Ma wrote:
>>> We encountered following panic. The scenario is the process is exiting
>>> and executing its task work. When closing dev node, the driver
>>> triggers a firmware reload according to device status. Because task->fs is
>> set to NULL in exit_fs(), panic happens.
>> I think this should be fixed somewhere else...
> Yes, for this panic, I also think driver is not perfect and need a fix. But kernel should not add the limitation like this...
>>> Task work is a common interface, we should not limite the resource the
>> user will utilize.
>> Exactly. And note that with this patch exit_mm()..disassociate_ctty() paths
>> can't use task works.
> I don't get this. Currently disassociate_ctty() is also called after exit_mm() and exit_task_work(). My patch didn't change this.


742- if (group_dead)
743: disassociate_ctty(1);
744- exit_task_namespaces(tsk);
745- exit_task_work(tsk);
746- exit_thread();

>> Not to mention that this patch moves exit_files() up, even before exit_mm(),
>> without any explanation.
> Moving exit_files() up is because exit_files() closes files and add tasks to task works.
>> Add Al. May be we can move exit_fs() down after exit_task_work(), I dunno,
>> but to me it would be better to change the driver.
> I'm OK with this suggestion to fix this issue. I'm not sure whether in the future task work users will access other resources and expose other issues.

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