On Wed, Oct 29, 2014 at 07:34:39AM -0700, Paul E. McKenney wrote: > On Wed, Oct 29, 2014 at 01:45:19PM +0000, Alexander Gordeev wrote: > > On Wed, Oct 29, 2014 at 05:47:29AM -0700, Paul E. McKenney wrote: > > > On Wed, Oct 29, 2014 at 12:07:07PM +0100, Alexander Gordeev wrote: > > > > Function rcu_is_cpu_rrupt_from_idle() is called from scheduling- > > > > clock interrupt handler to check if the current CPU was interrupted > > > > from idle. If true, it results in invocation of RCU callbacks. But > > > > the common hardware interrupt exit path also contains similar check > > > > and therefore the call to rcu_is_cpu_rrupt_from_idle() is redundant. > > > > > > By common hardware interrupt exit path, you are meaning the calls > > > to rcu_irq_exit()? If not, please let me know exactly what you > > > mean here. > > > > Yes, I mean rcu_irq_exit(). > > Unless you can get the indication of whether or not the original interrupt > came from userspace execution into rcu_irq_exit(), this will not work. > It will result in grace-period hangs on some configurations.
Okay, that was my concern wrt tree RCU. By contrast, tiny RCU does not seem able to hang a grace-period, isn't it? > Now, if you -can- get the userspace-execution indication into > rcu_irq_exit(), this might be of interest. However, it might be faster > to simply let the scheduling-clock interrupt do the job as it currently > does, especially for workloads with lots of interrupts. > > Or did you have something else in mind? Nope. I would even leave as is tiny RCU's rcu_is_cpu_rrupt_from_idle() for clarity then ;) > Thanx, Paul -- Regards, Alexander Gordeev [email protected] -- 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/
