Messages in this thread | | | Subject | Re: [PATCH RFC srcu] Expedite srcu_schedule_cbs_snp() callback invocation | From | Marc Zyngier <> | Date | Tue, 18 Apr 2017 18:43:05 +0100 |
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On 18/04/17 18:33, Paul E. McKenney wrote: > Although Tree SRCU does reduce delays when there is at least one > synchronize_srcu_expedited() invocation pending, srcu_schedule_cbs_snp() > still waits for SRCU_INTERVAL before invoking callbacks. Since > synchronize_srcu_expedited() now posts a callback and waits for > that callback to do a wakeup, this destroys the expedited nature of > synchronize_srcu_expedited(). > > This commit therefore invokes callbacks immediately at the end of the > grace period when there is at least one synchronize_srcu_expedited() > invocation pending. > > Reported-by: Marc Zyngier <marc.zyngier@arm.com> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index 1e54f91c2ff7..744ffdb79d23 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -447,7 +447,8 @@ static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp) > int cpu; > > for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) > - srcu_schedule_cbs_sdp(per_cpu_ptr(sp->sda, cpu), SRCU_INTERVAL); > + srcu_schedule_cbs_sdp(per_cpu_ptr(sp->sda, cpu), > + atomic_read(&sp->srcu_exp_cnt) ? 0 : SRCU_INTERVAL); > } > > /*
This fixes the issue I was observing, where UEFI in a KVM guest would take a x8 slowdown while it messes with some NOR flash emulation on arm64 (don't ask, this is horrible...). Anyway:
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Thanks again Paul!
M. -- Jazz is not dead. It just smells funny...
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