On Tue, 18 Mar 2003, Alan Stern wrote:

> On Tue, 18 Mar 2003, Oliver Neukum wrote:
> 
> > > > How can that be? The SCSI layer guarantees that no further requests are
> > > > issued while the error handler is running.
> > >
> > > Yes.  The synchronous API calls you are concerned about are made from a
> > > subroutine that is called directly by the error handler and that runs in
> > > the context of the error handler thread.  During the time this happens,
> > > the SCSI layer guarantees that no further requests are issued, either for
> > > block I/O or other error-handler stuff.
> > 
> > But what happens if the vm subsystem waits for this IO to complete as is
> > entirely legal with GFP_KERNEL allocations ?
> 
> You mean, what if the VM subsystem is blocked because it can't fulfill the
> error-handler's GFP_KERNEL allocation request until the I/O is completed
> and the I/O can't complete until the error-handler fixes things up?  I 
> don't know.  How do other subsystems handle this?

I just went back and re-read the kerneldoc explanation for the memory 
flags in usb_submit_urb().  You are correct.  I withdraw my objection to 
the patch.

Alan Stern



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