returning scsi I/O to OS from interrupt handler

[Parav Pandit <paravpandit@yahoo.com>]

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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