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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-06-26 10:49:50 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-07-25 13:04:46 -0700 |
| commit | 95335c0355834c16cc11f041a981ee6782dba2e9 (patch) | |
| tree | b1105efc30a1b319e21a6b5fb1ec040660e77e66 /kernel/rcu | |
| parent | c47e067a3c57835fe5ce24d50482f5c325a64efd (diff) | |
| download | linux-0-day-95335c0355834c16cc11f041a981ee6782dba2e9.tar.gz linux-0-day-95335c0355834c16cc11f041a981ee6782dba2e9.tar.xz | |
rcu: Check for NOCB CPUs and empty lists earlier in CB migration
The current CPU-hotplug RCU-callback-migration code checks
for the source (newly offlined) CPU being a NOCBs CPU down in
rcu_send_cbs_to_orphanage(). This commit simplifies callback migration a
bit by moving this check up to rcu_migrate_callbacks(). This commit also
adds a check for the source CPU having no callbacks, which eases analysis
of the rcu_send_cbs_to_orphanage() and rcu_adopt_orphan_cbs() functions.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f5acf34247fbb..aeea697d6f9f3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3862,10 +3862,6 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, { lockdep_assert_held(&rsp->orphan_lock); - /* No-CBs CPUs do not have orphanable callbacks. */ - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_is_nocb_cpu(rdp->cpu)) - return; - /* * Orphan the callbacks. First adjust the counts. This is safe * because _rcu_barrier() excludes CPU-hotplug operations, so it @@ -3935,6 +3931,9 @@ static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp) struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist)) + return; /* No callbacks to migrate. */ + raw_spin_lock_irqsave(&rsp->orphan_lock, flags); rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); rcu_adopt_orphan_cbs(rsp, flags); |