On Tue, 12 Mar 2019 07:09:23 -0700 "Paul E. McKenney" <[email protected]> wrote:
> On Tue, Mar 12, 2019 at 05:25:28PM +0530, Neeraj Upadhyay wrote: > > On 3/12/19 7:20 AM, Steven Rostedt wrote: > > >On Fri, 8 Mar 2019 15:16:18 +0530 > > >Neeraj Upadhyay <[email protected]> wrote: > > > > > >>Update the code to match the comment that self wakeup of > > >>grace period kthread is allowed from interrupt handler, and > > >>softirq handler, running in the grace period kthread's > > >>context. Present code allows self wakeups from all > > >>interrupt contexts - nmi, softirq and hardirq contexts. > > > > > >That's not actually the issue. But it appears that we return if we > > >simply have BH disabled, which I don't think we want, and we don't care > > >about NMI as NMI should never call this code. > > > > > >I think your patch is correct, but the change log is not. > > How about this? > > The current rcu_gp_kthread_wake() function uses in_interrupt() > and thus does a self-wakeup from all interrupt contexts, > including the pointless case where the GP kthread happens to be > running with bottom halves disabled, along with the impossible > case where the GP kthread is running within an NMI handler (you > are not supposed to invoke rcu_gp_kthread_wake() from within an > NMI handler. This commit therefore replaces the in_interrupt() > with in_irq(), so that the self-wakeups happen only from handlers > for hardware interrupts and softirqs. This also makes the code > match the comment. Acked-by: Steven Rostedt (VMware) <[email protected]> > > Thanx, Paul > > > >-- Steve > > > > > > > Hi Steve, sorry, I don't understand fully, why we want to not return > > in BH disabled case. From the commit logs and lkml discussion, there > > is a case where GP kthread is interrupted in the wait event path and > > rcu_gp_kthread_wake() is called in softirq handler (I am not sure > > about interrupt handler case; how rcu_gp_kthread_wake() is called > > from that path). BH disabled case isn't a case where the kthread is preempted. It's just that the kthread disabled BH, and thus we want to return. -- Steve
