On Tue, 25 Nov 2014, Marc Zyngier wrote: > Hi Daniel, > > On 25/11/14 17:26, Daniel Thompson wrote: > > irq_controller_lock is used for multiple purposes within the gic driver. > > Primarily it is used to make register read-modify-write sequences atomic. > > It is also used by gic_raise_softirq() in order that the big.LITTLE > > migration logic can figure out when it is safe to migrate interrupts > > between physical cores. > > > > The second usage of irq_controller_lock is difficult to discern when > > reviewing the code because the migration itself takes place outside > > the lock. > > > > This patch makes the second usage more explicit by splitting it out into > > a separate lock and providing better comments. > > While we're at it, how about an additional patch that would make this > lock disappear entirely when the big-little stuff is not compiled in, > which is likely to be the case on a lot of (dare I say most?) systems? > That will save expensive barriers that we definitely could do without.
For the record, I reviewed and ACKed a patch doing exactly that a while ago: http://lkml.org/lkml/2014/8/13/486 As far as I can see, no follo-ups happened. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
