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authorGerd Rausch2019-07-16 15:28:57 -0700
committerDavid S. Miller2019-07-17 12:06:51 -0700
commitc9467447fc50ec3715d8ec98f4da874fce539235 (patch)
tree51d23641565aed0c1bda2b866a56212f6669ace6 /net/rds/ib_mr.h
parent2c7da8e6b041a8df2661def81ac90c9c0c719909 (diff)
net/rds: Get rid of "wait_clean_list_grace" and add locking
Waiting for activity on the "clean_list" to quiesce is no substitute for proper locking. We can have multiple threads competing for "llist_del_first" via "rds_ib_reuse_mr", and a single thread competing for "llist_del_all" and "llist_del_first" via "rds_ib_flush_mr_pool". Since "llist_del_first" depends on "list->first->next" not to change in the midst of the operation, simply waiting for all current calls to "rds_ib_reuse_mr" to quiesce across all CPUs is woefully inadequate: By the time "wait_clean_list_grace" is done iterating over all CPUs to see that there is no concurrent caller to "rds_ib_reuse_mr", a new caller may have just shown up on the first CPU. Furthermore, <linux/llist.h> explicitly calls out the need for locking: * Cases where locking is needed: * If we have multiple consumers with llist_del_first used in one consumer, * and llist_del_first or llist_del_all used in other consumers, * then a lock is needed. Also, while at it, drop the unused "pool" parameter from "list_to_llist_nodes". Signed-off-by: Gerd Rausch <gerd.rausch@oracle.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/ib_mr.h')
-rw-r--r--net/rds/ib_mr.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/rds/ib_mr.h b/net/rds/ib_mr.h
index 42daccb7b5eb..ab26c20ed66f 100644
--- a/net/rds/ib_mr.h
+++ b/net/rds/ib_mr.h
@@ -98,6 +98,7 @@ struct rds_ib_mr_pool {
struct llist_head free_list; /* unused MRs */
struct llist_head clean_list; /* unused & unmapped MRs */
wait_queue_head_t flush_wait;
+ spinlock_t clean_lock; /* "clean_list" concurrency */
atomic_t free_pinned; /* memory pinned by free MRs */
unsigned long max_items;