linux-kernel - [PATCH 7/8] NTB: perf: Fix race condition when run with ntb

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Date:   Fri,  8 Jun 2018 18:08:18 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-ntb@...glegroups.com
Cc:     Jon Mason <jdmason@...zu.us>, Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Shuah Khan <shuah@...nel.org>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH 7/8] NTB: perf: Fix race condition when run with ntb_test

When running ntb_test, the script tries to run the ntb_perf test
immediately after probing the modules. Since adding multi-port support,
this fails seeing the new initialization procedure in ntb_perf
can not complete instantly.

To fix this we add a completion which is waited on when a test is
started. In this way, run can be written any time after the module is
loaded and it will wait for the initialization to complete instead of
sending an error.

Fixes: 5648e56d03fa ("NTB: ntb_perf: Add full multi-port NTB API support")
Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 drivers/ntb/test/ntb_perf.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/ntb/test/ntb_perf.c b/drivers/ntb/test/ntb_perf.c
index 6285cb8515ac..8e2b7630ecc9 100644
--- a/drivers/ntb/test/ntb_perf.c
+++ b/drivers/ntb/test/ntb_perf.c
@@ -158,6 +158,8 @@ struct perf_peer {
 	/* NTB connection setup service */
 	struct work_struct	service;
 	unsigned long		sts;
+
+	struct completion init_comp;
 };
 #define to_peer_service(__work) \
 	container_of(__work, struct perf_peer, service)
@@ -549,6 +551,7 @@ static int perf_setup_outbuf(struct perf_peer *peer)
 
 	/* Initialization is finally done */
 	set_bit(PERF_STS_DONE, &peer->sts);
+	complete_all(&peer->init_comp);
 
 	return 0;
 }
@@ -639,6 +642,7 @@ static void perf_service_work(struct work_struct *work)
 		perf_setup_outbuf(peer);
 
 	if (test_and_clear_bit(PERF_CMD_CLEAR, &peer->sts)) {
+		init_completion(&peer->init_comp);
 		clear_bit(PERF_STS_DONE, &peer->sts);
 		if (test_bit(0, &peer->perf->busy_flag) &&
 		    peer == peer->perf->test_peer) {
@@ -1046,8 +1050,9 @@ static int perf_submit_test(struct perf_peer *peer)
 	struct perf_thread *pthr;
 	int tidx, ret;
 
-	if (!test_bit(PERF_STS_DONE, &peer->sts))
-		return -ENOLINK;
+	ret = wait_for_completion_interruptible(&peer->init_comp);
+	if (ret < 0)
+		return ret;
 
 	if (test_and_set_bit_lock(0, &perf->busy_flag))
 		return -EBUSY;
@@ -1413,6 +1418,7 @@ static int perf_init_peers(struct perf_ctx *perf)
 			peer->gidx = pidx;
 		}
 		INIT_WORK(&peer->service, perf_service_work);
+		init_completion(&peer->init_comp);
 	}
 	if (perf->gidx == -1)
 		perf->gidx = pidx;
-- 
2.11.0