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RDS: Rewrite rds_send_drop_to() for clarity
This function has been the source of numerous bugs; it's just too complicated. Simplified to nest spinlocks cleanly within the second loop body, and kick out early if there are no rms to drop. This will be a little slower because conn lock is grabbed for each entry instead of "caching" the lock across rms, but this should be entirely irrelevant to fastpath performance. Signed-off-by: Andy Grover <andy.grover@oracle.com>
This commit is contained in:
parent
35b52c7053
commit
7c82eaf00e
1 changed files with 31 additions and 37 deletions
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@ -619,9 +619,8 @@ void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in *dest)
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{
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{
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struct rds_message *rm, *tmp;
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struct rds_message *rm, *tmp;
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struct rds_connection *conn;
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struct rds_connection *conn;
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unsigned long flags, flags2;
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unsigned long flags;
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LIST_HEAD(list);
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LIST_HEAD(list);
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int wake = 0;
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/* get all the messages we're dropping under the rs lock */
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/* get all the messages we're dropping under the rs lock */
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spin_lock_irqsave(&rs->rs_lock, flags);
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spin_lock_irqsave(&rs->rs_lock, flags);
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@ -631,58 +630,53 @@ void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in *dest)
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dest->sin_port != rm->m_inc.i_hdr.h_dport))
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dest->sin_port != rm->m_inc.i_hdr.h_dport))
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continue;
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continue;
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wake = 1;
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list_move(&rm->m_sock_item, &list);
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list_move(&rm->m_sock_item, &list);
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rds_send_sndbuf_remove(rs, rm);
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rds_send_sndbuf_remove(rs, rm);
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clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
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clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
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}
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}
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/* order flag updates with the rs lock */
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/* order flag updates with the rs lock */
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if (wake)
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smp_mb__after_clear_bit();
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smp_mb__after_clear_bit();
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spin_unlock_irqrestore(&rs->rs_lock, flags);
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spin_unlock_irqrestore(&rs->rs_lock, flags);
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conn = NULL;
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if (list_empty(&list))
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return;
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/* now remove the messages from the conn list as needed */
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/* Remove the messages from the conn */
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list_for_each_entry(rm, &list, m_sock_item) {
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list_for_each_entry(rm, &list, m_sock_item) {
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/* We do this here rather than in the loop above, so that
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* we don't have to nest m_rs_lock under rs->rs_lock */
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conn = rm->m_inc.i_conn;
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spin_lock_irqsave(&rm->m_rs_lock, flags2);
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spin_lock_irqsave(&conn->c_lock, flags);
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/* If this is a RDMA operation, notify the app. */
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/*
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* Maybe someone else beat us to removing rm from the conn.
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* If we race with their flag update we'll get the lock and
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* then really see that the flag has been cleared.
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*/
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if (!test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags)) {
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spin_unlock_irqrestore(&conn->c_lock, flags);
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continue;
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}
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/*
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* Couldn't grab m_rs_lock in top loop (lock ordering),
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* but we can now.
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*/
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spin_lock(&rm->m_rs_lock);
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spin_lock(&rs->rs_lock);
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spin_lock(&rs->rs_lock);
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__rds_rdma_send_complete(rs, rm, RDS_RDMA_CANCELED);
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__rds_rdma_send_complete(rs, rm, RDS_RDMA_CANCELED);
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spin_unlock(&rs->rs_lock);
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spin_unlock(&rs->rs_lock);
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rm->m_rs = NULL;
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rm->m_rs = NULL;
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spin_unlock_irqrestore(&rm->m_rs_lock, flags2);
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spin_unlock(&rm->m_rs_lock);
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/*
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* If we see this flag cleared then we're *sure* that someone
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* else beat us to removing it from the conn. If we race
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* with their flag update we'll get the lock and then really
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* see that the flag has been cleared.
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*/
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if (!test_bit(RDS_MSG_ON_CONN, &rm->m_flags))
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continue;
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if (conn != rm->m_inc.i_conn) {
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if (conn)
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spin_unlock_irqrestore(&conn->c_lock, flags);
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conn = rm->m_inc.i_conn;
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spin_lock_irqsave(&conn->c_lock, flags);
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}
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if (test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags)) {
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list_del_init(&rm->m_conn_item);
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list_del_init(&rm->m_conn_item);
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rds_message_put(rm);
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rds_message_put(rm);
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}
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}
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if (conn)
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spin_unlock_irqrestore(&conn->c_lock, flags);
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spin_unlock_irqrestore(&conn->c_lock, flags);
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}
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if (wake)
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rds_wake_sk_sleep(rs);
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rds_wake_sk_sleep(rs);
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while (!list_empty(&list)) {
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while (!list_empty(&list)) {
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