On Wed, 19 Sep 2007 15:49:24 -0400 "Dmitry Torokhov" <[EMAIL PROTECTED]> wrote:
> On 9/19/07, Peter Zijlstra <[EMAIL PROTECTED]> wrote: > > On Wed, 19 Sep 2007 14:49:56 -0400 "Dmitry Torokhov" > > <[EMAIL PROTECTED]> wrote: > > > > > On 9/19/07, Paul E. McKenney <[EMAIL PROTECTED]> wrote: > > > > > > PS to previous -- any problem with inserting rcu_read_lock() and > > > > rcu_read_unlock() around the portion of the IRQ handler that has > > > > these accesses? > > > > > > > > > > I guess I could but it is an extra lock that needs to be managed and > > > given the fact that it is not really needed (other to make a newly > > > developed tool happy) I am hestsant to do that. > > > > As is, these sites are a bug in -rt and we'll need to fix them anyway. > > > > As for the code you pointed me to, the i8042 driver, it seems to play > > way to funny tricks for a simple 'slow' driver. > > Even "slow" driver should try not to slow down the rest of the system > if it can help it. I am sorry if the thing it does do not quite fit in > with the changes you are proposing but it does not make the exeisting > code invalid. > > > > > If you replace the spin_lock() + sync_sched(), with rcu_read_lock() + > > rcu_call() it should work again without adding an extra lock. > > > > Except that I need spin_lock_irq for other reasons. I could take the > same lock in write-side code and not use RCU at all but using RCU > allows opening/closing input devices without slowing down interrupt > handlers so why not use it? If the IRQ handler does rcu_read_lock(),unlock() and the i8042_stop() function does sync_rcu() instead of _sched(), it should be good again. It will not affect anything else than the task that calls _stop(). And even there the only change is that the sleep might be a tad longer. I find it curious that a driver that is 'low performant' and does not suffer lock contention pioneers locking schemes. I agree with optimizing, but this is not the place to push the envelope. - 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/
