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: linux-rdma-owner@xxxxxxxxxxxxxxx <linux-rdma-
> owner@xxxxxxxxxxxxxxx> On Behalf Of Leon Romanovsky
> Sent: Tuesday, May 12, 2020 1:55 AM
> To: Dalessandro, Dennis <dennis.dalessandro@xxxxxxxxx>
> Cc: jgg@xxxxxxxx; 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:
> 
> I was under impression that kernel reboot should follow same logic as
> module removal. This is what graceful reboot will do anyway. Can you please
> give me a link where I can read about difference in those flows?
> 
I used to think the same. However, by adding traces to the hfi driver, I found out that the shutdown function of the pci_driver was called when typing "reboot"  while the remove function  of the pci_driver was called when typing "modprobe -r hfi1". 

I am not an expert on kernel reboot and can someone give some hints?

Kaike








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