RE: [PATCH for-rc or next 1/3] IB/hfi1: Do not destroy hfi1_wq when the device is shut down

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> -----Original Message-----
> From: Jason Gunthorpe <jgg@xxxxxxxx>
> Sent: Tuesday, May 19, 2020 8:27 PM
> To: Dalessandro, Dennis <dennis.dalessandro@xxxxxxxxx>
> Cc: dledford@xxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; Marciniszyn, Mike
> <mike.marciniszyn@xxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Wan, Kaike
> <kaike.wan@xxxxxxxxx>
> Subject: Re: [PATCH for-rc or next 1/3] IB/hfi1: Do not destroy hfi1_wq when
> the device is shut down
> 
> On Mon, May 11, 2020 at 11:13:15PM -0400, Dennis Dalessandro wrote:
> > From: Kaike Wan <kaike.wan@xxxxxxxxx>
> >
> > The workqueue hfi1_wq is destroyed in function shutdown_device(),
> > which is called by either shutdown_one() or remove_one(). The function
> > shutdown_one() is called when the kernel is rebooted while
> > remove_one() is called when the hfi1 driver is unloaded. When the
> > kernel is rebooted, hfi1_wq is destroyed while all qps are still
> > active, leading to a kernel crash:
> 
> AFAIK the purpose of shutdown is to stop all in progress DMAs.
> 
> If devices are wildly doing DMA during the shutdown process then all manner
> of things can fail, including kexecing into another kernel.
> 
> Do you achive that with these shutdown handlers?

We did try to shut down the hardware and will address some software issues in next revision.

> 
> It does make sense that the work queue would not be destroyed in
> shutdown, but I'm surprised it doesn't flush it?
Will do.

Kaike




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