Commit-ID: 38d30b336ccf8ee98e0e494a13738a0fade5a5e6
Gitweb: http://git.kernel.org/tip/38d30b336ccf8ee98e0e494a13738a0fade5a5e6
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 1 Dec 2016 09:55:27 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 23 Jan 2017 11:44:18 -0800
rcu: Adjust FQS offline checks for exact online-CPU detection
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 <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
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 d8245cb..6e4b1dc 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;
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|