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Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree

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On 9/22/2016 12:05 AM, Thomas Gleixner wrote:
> B1;2802;0cOn Wed, 21 Sep 2016, Santosh Shilimkar wrote:
>> I requested you to include this patch but now am not sure anymore.
>> Looks like there are almost 30 more users which are directly
>> tweaking 'tasklet_struct' fields and calling other APIs. Hunting them
>> and fixing them probably would be an exercise and also those changes
>> needs those changed drivers to be tested.
>>
>> What do you suggest ? At least this patch needs to be dropped as of now
>> till we can have complete coverage for those bad users.
>
> Yes, it needs to be dropped. Stephen, can you please revert it from next?
>
> How to fix this: The only way is to review all tasklet usage sites for
> creative abuse and then fix them one by one. This needs to be done anyway
> because those are ticking timebombs even without changes in the core
> code. I looked at one of the offenders and it's broken today, it's just
> protected by the extremly low probablity to hit the wreckage case.
>
> What you can do to coerce the developers/maintainers of offending code into
> looking at the mess they created/merged is to implement accessors for the
> tasklet struct fields and replace the open coded fiddling with them.
>
> Once that is done, rename the struct fields to something which is absurd
> enough to type.  But don't worry, you will find people doing that. I
> catched a few brainwrecks who actually used:
>
>  irqdesc->core_internal_state__do_not_mess_with_it
>
> in their code.
>
> Now after having everything converted to accessors, you can add sanity
> checks into the accessors and emit WARN_ONCE() when they are used in the
> wrong context. That'll make them look and explain why they think that
> fiddling in the internals is a good idea.
>
Thanks Thomas for suggestion and looking into it. Sounds a good plan
to me to tackle this mess. I will give a try and hopefully with help
of those maintainers come up with a series first to fix the
existing bad users. As you said, fixing core will be simple after that.

Regards,
Santosh

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Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-09-21 07:20 +0200
  Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-09-21 10:20 +0200
    Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-09-21 19:30 +0200
      Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-09-22 02:50 +0200
        Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-09-22 04:40 +0200
          Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm  tree Thomas Gleixner <tglx@linutronix.de> - 2016-09-22 09:10 +0200
            Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm tree Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-09-22 18:20 +0200
            Re: + softirq-fix-tasklet_kill-and-its-users.patch added to -mm  tree Stephen Rothwell <sfr@canb.auug.org.au> - 2016-09-23 01:40 +0200

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