On Thu, 18 Oct 2018 18:26:45 -0700 Joel Fernandes <j...@joelfernandes.org> wrote:
> Yes, local_irq_restore is light weight, and does not check for reschedules. > > I was thinking of case where ksoftirqd is woken up, but does not run unless > we set the NEED_RESCHED flag. But that should get set anyway since probably > ksoftirqd is of high enough priority than the currently running task.. > > Roughly speaking the scenario could be something like: > > rcu_read_lock(); > <-- IPI comes in for the expedited GP, sets exp_hint > local_irq_disable(); > // do a bunch of stuff > rcu_read_unlock(); <-- This calls the rcu_read_unlock_special which raises > the soft irq, and wakesup softirqd. If softirqd is of higher priority than the current running task, then the try_to_wake_up() will set NEED_RESCHED of the current task here. -- Steve > local_irq_enable(); > > // Now ksoftirqd is ready to run but we don't switch into the > // scheduler for sometime because tif_need_resched() returns false and > // any cond_resched calls do nothing. So we potentially spend lots of > // time before the next scheduling event. > > You think this should not be an issue?
