From mboxrd@z Thu Jan  1 00:00:00 1970
From: Parav Pandit <paravpandit@yahoo.com>
Subject: Re: returning scsi I/O to SCSI mid layer from Fast IRQ  context
Date: Thu, 30 Aug 2007 02:45:42 -0700 (PDT)
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Let me simplify and ask in different way.

1. Can I return a scsi I/O by invoking scsi_done()
from the Fast IRQ context in the Low level SCSI HBA
driver?

2. Is the interrupt handler right place to call
scsi_done() and invoke SCSI mid layer? or should I
defer to the DPC thread context?

Parav



--- Parav Pandit <paravpandit@yahoo.com> wrote:

> Hi,
> 
> A low level SCSI HBA driver can return the I/O back
> to
> the OS from various paths.
> 
> Some of the common possible paths
> 1, enqueue_command itself
> 2. Timer handler (at the time of command timeout)
> 3. Interrupt handler (when a response is received
> from
> the storage)
> 4. DPC handler thread.
> 
> Whenever an I/O is returned from the interrupt
> handler
> by invoking scsi_done callback function, it will
> invoke the SCSI mid layer.
> 
> 1. Is it good practice to return call scsi_done
> callback function from Interrupt handler? 
> If no, may I know the implications of doing that?
> (other then blocking the interrupt context for a
> longer time)
> 
> 2. if multiple I/Os are returned in a single
> interrupt, how many  commands should be returned by
> calling scsi_done before shifting to dpc thread?
> 
> Regards,
> Parav Pandit
> 
> 
> 
>        
>
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