Messages in this thread | | | Date | Tue, 12 Mar 2019 08:36:44 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu/tree: Fix self wakeups for grace period kthread |
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On Tue, Mar 12, 2019 at 10:56:08AM -0400, Steven Rostedt wrote: > On Tue, 12 Mar 2019 07:09:23 -0700 > "Paul E. McKenney" <paulmck@linux.ibm.com> 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 <neeraju@codeaurora.org> 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) <rostedt@goodmis.org>
Applied, thank you!
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 >
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