[openib-general] SDP_CONN_LOCK

[Michael S. Tsirkin]

Quoting r. Libor Michalek <libor at topspin.com>:
> Subject: Re: [openib-general] SDP_CONN_LOCK
> 
> On Thu, Feb 17, 2005 at 05:35:17PM +0200, Michael S. Tsirkin wrote:
> > Hi, Libor!
> > Could you please explain what are the SDP_CONN_LOCK
> > and friends doing in SDP?
> > 
> > It seems they just implement exclusive access to socket,
> > but if so, why is a simple semaphore or mutex not used?
> 
>   They do implement exclusive access to the socket, but they implement
> exclusive access from both process and irq context, which is why a
> semaphore was not used. In interrupt context SDP_CONN_LOCK_BH is used
> to lock the connection, look in sdp_cq_event_handler() for it's use,
> and in process context SDP_CONN_LOCK is used.

I dont really understand how it works.
When an interrupt arrives while users != 0, it seems you are
calling scheduler().
What is sdp_conn_internal_lock doing? I understand it is to be called
from interrupt context, but how can it call scheduler() then?



-- 
MST - Michael S. Tsirkin