mpslsi0 : Trying sleep, but thread marked as sleeping prohibited

[Desai, Kashyap]

Adding Ed Schouten and Jorg Wunsch  as I see there are author of msleep/mtx related APIs.

> -----Original Message-----
> From: Desai, Kashyap
> Sent: Wednesday, February 22, 2012 7:37 PM
> To: freebsd-scsi at freebsd.org; freebsd-stable
> Cc: 'Kenneth D. Merry'; McConnell, Stephen; Justin T. Gibbs
> Subject: mpslsi0 : Trying sleep, but thread marked as sleeping
> prohibited
> 
> Hi,
> 
> I am doing some code changes in mps dirver. While working on those
> changes, I come to know about something which is new to me.
> Some expert help is required to clarify my doubt.
> 
> 1. When any irq is register with FreeBSD OS, it sets " TDP_NOSLEEPING"
> pflag. It means though irq in freebsd is treated as thread,
> We cannot sleep in IRQ because of " "TDP_NOSLEEPING " set.
> 2. In mps driver we have below code snippet in ISR routine.
> 
> 
>     mps_dprint(sc, MPS_TRACE, "%s\n", __func__);
>     mps_lock(sc);
>     mps_intr_locked(data);
>     mps_unlock(sc);
> 
> I wonder why there is no issue with above code ? Theoretical we cannot
> sleep in ISR. (as explained in #1)
> Any thoughts ?
> 
> 
> 3. I recently added few place msleep() instead of DELAY in ISR context
> and I see
> " Trying sleep, but thread marked as sleeping prohibited".
> 
> 
> ` Kashyap