IB/core: use RCU for uverbs id lookup
The current implementation gets a spin_lock, and at any scale with
qib and hfi1 post send, the lock contention grows exponentially
with the number of QPs.
idr_find() is RCU compatibile, so read doesn't need the lock.
Change to use rcu_read_lock() and rcu_read_unlock() in
__idr_get_uobj().
kfree_rcu() is used to insure a grace period between the
idr removal and actual free.
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 9a68a19..120da1d 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1271,6 +1271,7 @@
int id; /* index into kernel idr */
struct kref ref;
struct rw_semaphore mutex; /* protects .live */
+ struct rcu_head rcu; /* kfree_rcu() overhead */
int live;
};