On 9/16/10 2:25 PM, Andi Kleen wrote: >> I asked James about getting Vasu's unlocked_qcmds=1 patch merged, but he >> convinced me that doing conditional locking while is very simple, is not >> the proper way for getting this resolved in mainline code. I think in >> the end this will require a longer sit down to do a wholesale conversion >> of all existing SCSI LLD drivers, and identifing the broken ones that >> still need a struct Scsi_Host->host_lock'ed SHT->queuecommand() for >> whatever strange & legacy reasons. > > The standard way to do that would be to first move the lock down > into the drivers (similar to how it has been done with the BKL). > This would be a fairly mechanic mindless patch. Lots of typing, > but not really a lot of real code review needed. > > Then next step the drivers who know they don't want it can remove it. > > -Andi I see problems with this, but maybe I'm missing something. It seems to me we can't completely move the host lock down into the drivers since its a shared lock between SCSI and the drivers now. If we just have SCSI drop the lock and have the LLD reacquire it, that may open up a hole that some LLDs might not tolerate. It also hurts performance for the LLDs that want to keep the lock for the duration of queuecommand() by adding an extra unlock/lock. Obviously, some LLDs may depend on that shared lock being held, without a drop just before the call. So, I think the flag approach is OK, or wait until the wholesale approach can be done. Regards, Joe -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
