diff options
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-04-18 10:28:31 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-04-21 05:59:27 -0700
commit0497b489b8255054f113fd31faeb72f6dbc50a68 (patch)
parentsrcu: Parallelize callback handling (diff)
srcu: Expedite srcu_schedule_cbs_snp() callback invocation
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 destruction became apparent to Marc Zyngier in the guise of a guest-OS bootup slowdown from five seconds to no fewer than forty seconds. This commit therefore invokes callbacks immediately at the end of the grace period when there is at least one synchronize_srcu_expedited() invocation pending. This brought Marc's guest-OS bootup times back into the realm of reason. Reported-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com>
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 12feeca18f46..9ecf0acc18eb 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -442,7 +442,8 @@ 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);