Messages in this thread | | | Subject | Re: [PATCH] rcu/tree: Fix self wakeups for grace period kthread | From | Neeraj Upadhyay <> | Date | Tue, 12 Mar 2019 17:25:28 +0530 |
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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. > > -- 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).
https://github.com/torvalds/linux/commit/1d1f898df6586c5ea9aeaf349f13089c6fa37903
Thanks Neeraj > >> >> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> >> --- >> kernel/rcu/tree.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c >> index acd6ccf..57cac6d 100644 >> --- a/kernel/rcu/tree.c >> +++ b/kernel/rcu/tree.c >> @@ -1585,7 +1585,7 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) >> static void rcu_gp_kthread_wake(void) >> { >> if ((current == rcu_state.gp_kthread && >> - !in_interrupt() && !in_serving_softirq()) || >> + !in_irq() && !in_serving_softirq()) || >> !READ_ONCE(rcu_state.gp_flags) || >> !rcu_state.gp_kthread) >> return; >
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