Commit 7ec99de36f40 ("rcu: Provide exact CPU-online tracking for RCU"),
as its title suggests, got rid of RCU's remaining CPU-hotplug timing
guesswork. This commit therefore removes the one-jiffy kludge that was
used to paper over this guesswork.
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <j...@joshtriplett.org>
---
kernel/rcu/tree.c | 17 ++---------------
1 file changed, 2 insertions(+), 15 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 37a1d91f1ec7..c49bb791aeca 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1276,21 +1276,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
return 1;
}
- /*
- * Check for the CPU being offline, but only if the grace period
- * is old enough. We don't need to worry about the CPU changing
- * state: If we see it offline even once, it has been through a
- * quiescent state.
- *
- * The reason for insisting that the grace period be at least
- * one jiffy old is that CPUs that are not quite online and that
- * have just gone offline can still execute RCU read-side critical
- * sections.
- */
- if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
- return 0; /* Grace period is not old enough. */
- barrier();
- if (cpu_is_offline(rdp->cpu)) {
+ /* Check for the CPU being offline. */
+ if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp))) {
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl"));
rdp->offline_fqs++;
return 1;
--
2.5.2
