On Tue, Apr 12, 2011 at 07:14:28AM +1000, NeilBrown wrote: > > My understanding of that was that the calling requirement of > __elv_add_request is that the queue spinlock is held and that interrupts are > disabled. > So rather than possible enabling and disabling interrupts several times as > different queue are handled, the code just disabled interrupts once, and > then just take the spinlock once for each different queue. > > The whole point of the change to plugging was to take locks less often. > Disabling interrupts less often is presumably an analogous goal. > > Though I agree that a comment would help. > > q = NULL; > + /* Disable interrupts just once rather than using spin_lock_irq/sin_unlock_irq > * variants > */ > local_irq_save(flags); > > > assuming my analysis is correct. Your explanation does make sense to be now that you explain it. I didn't even thing of that variant before. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
