On Wed, Aug 12, 2009 at 12:22:34PM +0300, Avi Kivity wrote: > On 08/12/2009 12:11 PM, Gleb Natapov wrote: >> On Wed, Aug 12, 2009 at 11:29:00AM +0300, Avi Kivity wrote: >> >>> On 08/11/2009 03:31 PM, Gleb Natapov wrote: >>> >>>> Change irq_lock from mutex to spinlock. We do not sleep while holding >>>> it. >>>> >>>> >>> But why change? >>> >>> >> Isn't it more lightweight? For the remaining use of the lock it doesn't >> really matters, but if I see mutex used somewhere I assume there are >> users that sleeps. >> > > Before the recent change, a mutex was more expensive if there was > contention (waiter would schedule out). Recently the mutex code was > changed to spin while the holder was running. > >>> The only motivation I can see is to allow injection from irqfd and >>> interrupt contexts without requiring a tasklet/work. But that needs >>> spin_lock_irqsave(), not spin_lock(). >>> >>> >> After this series the lock is used only to protect modification of irq >> table, add/delete of ack notifiers and irq source id allocator. None of >> this affects injection from irqfd. >> >> > > Then it can be definitely left as mutex. > OK. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
