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Re: [dm-devel] dm-mpath: do not change SCSI device handler




On Thu, 4 Apr 2013, Mikulas Patocka wrote:

> On Thu, 4 Apr 2013, Mike Snitzer wrote:
> 
> > I'm suggesting that switching the scsi_dh is not something that will be
> > done on a system that is suffering from serious memory contention.
> > 
> > But I think we need to get back to analyzing the scsi_dh change you
> > mentioned before with tracking counts, etc.
> 
> When I look at the code, I see module_put(THIS_MODULE) in all scsi device 
> handlers. Moreover, there are many 'module_put(THIS_MODULE)' over the 
> whole kernel. It seems buggy, because when the function module_put 
> returns, reschedule happens, module is unloaded, the process that called 
> module_put(THIS_MODULE) is scheduled back again, crash happens because we 
> are running a code that no longer exists. Is it a bug or is there some 
> trick that prevents the kernel from crashing in this scenario?
> 
> Mikulas

I found this 
http://lkml.indiana.edu/hypermail/linux/kernel/1111.0/00218.html saying 
that they don't care about module unloading races ...

Mikulas


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