linux-kernel - Re: [PATCH 10/10] Replace tasklets with workqueues

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Message-ID: <385139f2-0d31-1148-95c0-a6e6768ab413@os.inf.tu-dresden.de>
Date:   Tue, 30 Jul 2019 21:20:23 +0200
From:   Maksym Planeta <mplaneta@...inf.tu-dresden.de>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Moni Shoua <monis@...lanox.com>,
        Doug Ledford <dledford@...hat.com>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/10] Replace tasklets with workqueues



On 25/07/2019 20:50, Jason Gunthorpe wrote:
> On Thu, Jul 25, 2019 at 04:36:20PM +0200, Maksym Planeta wrote:
>> Is this one better?
>>
>> Replace tasklets with workqueues in rxe driver. The reason for this
>> replacement is that tasklets are supposed to run atomically, although the
>> actual code may block.
>>
>> Modify the SKB destructor for outgoing SKB's to schedule QP tasks only if
>> the QP is not destroyed itself.
>>
>> Add a variable "pending_skb_down" to ensure that reference counting for a QP
>> is decremented only when QP access related to this skb is over.
>>
>> Separate part of pool element cleanup code to allow this code to be called
>> in the very end of cleanup, even if some of cleanup is scheduled for
>> asynchronous execution. Example, when it was happening is destructor for a
>> QP.
>>
>> Disallow calling of task functions "directly". This allows to simplify logic
>> inside rxe_task.c
>>
>> Schedule rxe_qp_do_cleanup onto high-priority system workqueue, because this
>> function can be scheduled from normal system workqueue.
>>
>> Before destroying a QP, wait until all references to this QP are gone.
>> Previously the problem was that outgoing SKBs could be freed after the QP
>> these SKBs refer to is destroyed.
>>
>> Add blocking rxe_run_task to replace __rxe_do_task that was calling task
>> function directly.
> 
> Mostly but it would also be good to describe the use after free and
> races more specifically
> 

These situations are described in the cover letter (PATCH 00/10). Do you 
need a more detailed description than that?

> Jason
> 

-- 
Regards,
Maksym Planeta