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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2016-12-01 09:55:27 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-01-23 11:44:18 -0800
commit38d30b336ccf8ee98e0e494a13738a0fade5a5e6 (patch)
treef3d753934aa5014c7ef5837130d4c1229b42b6e6 /kernel/rcu
parent3a19b46a5c17b12ef0691df19c676ba3da330a57 (diff)
downloadlinux-38d30b336ccf8ee98e0e494a13738a0fade5a5e6.tar.bz2
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@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c17
1 files changed, 2 insertions, 15 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d8245cbd08f9..6e4b1dcebeb2 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;