Re: [RFC] How to fix an async scan - rmmod race?

[Bart Van Assche <bvanassche@xxxxxxx>]

On 04/05/12 13:58, Tomas Henzl wrote:

> When a rmmod is tried then in some cases the kernel is not able to handle a paging request:
> [  727.154296] BUG: unable to handle kernel paging request at ffffffffa01874b8
> From what I observerved it happens when when we call the rmmod only a while after a modprobe
> (in this case it is the mpt2sas driver). More accurately said, it happens when rmmod is called
> while scsi async is still at work. The driver is removed but the scsi_host_template is still filled
> with now invalid pointers, in this case it is most likely the hostt->scan_finished which causes the BUG.


Are you sure the above analysis is correct ? I've triggered several
million device removal events with ib_srp but I haven't ever seen the
above crash. Maybe your patch for the SCSI core is hiding a race in the
mpt2sas device removal code.

Bart.
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