[PATCH net] net: qrtr: ns: retry service announcements on -EAGAIN

[Joonhoe Kim <26rote@gmail.com>]

Since commit 544d85de4dc2 ("net: qrtr: Send HELLO message on endpoint
register"), qrtr_node_enqueue() returns -EAGAIN for every packet but
HELLO until our HELLO has gone out to the node. The HELLO is retried,
but the NEW_SERVER announcements sent in reply to the remote's HELLO
are not, so a service registered before the remote came up is never
announced to it.

On Kaanapali the modem sends its HELLO before it accepts ours. With
rmtfs started first, the modem never learns about rmtfs and its
watchdog resets the SoC about 40 s later.

Retry each announcement for up to 10 s while it fails with -EAGAIN.
announce_servers() runs from the name service worker, which can sleep.

Fixes: 544d85de4dc2 ("net: qrtr: Send HELLO message on endpoint register")
Cc: stable@vger.kernel.org
Signed-off-by: Joonhoe Kim <26rote@gmail.com>
---
Tested on a Lenovo Legion Tab Y700 Gen 5 (out-of-tree board support)
with rmtfs started before the modem: without this patch the SoC resets;
with it the announcement goes out on the first retry and the modem
stays up. Starting rmtfs after the modem avoids the problem, but
distribution units start rmtfs first and let it boot the modem.

 net/qrtr/ns.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index bcb090ee79d4..33a9c4449d6f 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2020, Linaro Ltd.
  */
 
+#include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/qrtr.h>
 #include <linux/workqueue.h>
@@ -226,7 +227,13 @@ static int announce_servers(struct sockaddr_qrtr *sq)
 
 	/* Announce the list of servers registered in this node */
 	xa_for_each(&node->servers, index, srv) {
+		unsigned long timeout = jiffies + 10 * HZ;
+
 		ret = service_announce_new(sq, srv);
+		while (ret == -EAGAIN && time_before(jiffies, timeout)) {
+			msleep(100);
+			ret = service_announce_new(sq, srv);
+		}
 		if (ret < 0) {
 			if (ret == -ENODEV)
 				continue;
-- 
2.43.0