netdev - [PATCH net-next v2 1/4] RDS: limit the number of times we loop in rds_send

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Date:   Thu, 15 Aug 2019 07:42:03 -0700
From:   Gerd Rausch <gerd.rausch@...cle.com>
To:     Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        rds-devel@....oracle.com
Cc:     David Miller <davem@...emloft.net>
Subject: [PATCH net-next v2 1/4] RDS: limit the number of times we loop in
 rds_send_xmit

From: Chris Mason <chris.mason@...cle.com>
Date: Fri, 3 Feb 2012 11:07:54 -0500

This will kick the RDS worker thread if we have been looping
too long.

Original commit from 2012 updated to include a change by
Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
that triggers "must_wake" if "rds_ib_recv_refill_one" fails.

Signed-off-by: Gerd Rausch <gerd.rausch@...cle.com>
---
 net/rds/ib_recv.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 3cae88cbdaa0..1a8a4a760b84 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -385,6 +385,7 @@ void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
 	unsigned int posted = 0;
 	int ret = 0;
 	bool can_wait = !!(gfp & __GFP_DIRECT_RECLAIM);
+	bool must_wake = false;
 	u32 pos;
 
 	/* the goal here is to just make sure that someone, somewhere
@@ -405,6 +406,7 @@ void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
 		recv = &ic->i_recvs[pos];
 		ret = rds_ib_recv_refill_one(conn, recv, gfp);
 		if (ret) {
+			must_wake = true;
 			break;
 		}
 
@@ -423,6 +425,11 @@ void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
 		}
 
 		posted++;
+
+		if ((posted > 128 && need_resched()) || posted > 8192) {
+			must_wake = true;
+			break;
+		}
 	}
 
 	/* We're doing flow control - update the window. */
@@ -445,10 +452,13 @@ void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
 	 * if we should requeue.
 	 */
 	if (rds_conn_up(conn) &&
-	    ((can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
+	    (must_wake ||
+	    (can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
 	    rds_ib_ring_empty(&ic->i_recv_ring))) {
 		queue_delayed_work(rds_wq, &conn->c_recv_w, 1);
 	}
+	if (can_wait)
+		cond_resched();
 }
 
 /*
-- 
2.22.1