blob: a5187b80b40bbce18c0cd86ecf30f208751cf378 [file] [log] [blame]
Arvind M8e87d852018-01-29 00:04:29 -08001From 3d5be1891644e6f254e2ff1022428d60d075165a Mon Sep 17 00:00:00 2001
Allen Martin685e0f82016-07-26 19:34:29 -07002From: Marc Kleine-Budde <mkl@pengutronix.de>
3Date: Wed, 5 Mar 2014 00:49:47 +0100
Arvind M10268e72017-12-04 22:18:06 -08004Subject: [PATCH 020/366] net: sched: Use msleep() instead of yield()
Allen Martin685e0f82016-07-26 19:34:29 -07005
6On PREEMPT_RT enabled systems the interrupt handler run as threads at prio 50
7(by default). If a high priority userspace process tries to shut down a busy
8network interface it might spin in a yield loop waiting for the device to
9become idle. With the interrupt thread having a lower priority than the
10looping process it might never be scheduled and so result in a deadlock on UP
11systems.
12
13With Magic SysRq the following backtrace can be produced:
14
15> test_app R running 0 174 168 0x00000000
16> [<c02c7070>] (__schedule+0x220/0x3fc) from [<c02c7870>] (preempt_schedule_irq+0x48/0x80)
17> [<c02c7870>] (preempt_schedule_irq+0x48/0x80) from [<c0008fa8>] (svc_preempt+0x8/0x20)
18> [<c0008fa8>] (svc_preempt+0x8/0x20) from [<c001a984>] (local_bh_enable+0x18/0x88)
19> [<c001a984>] (local_bh_enable+0x18/0x88) from [<c025316c>] (dev_deactivate_many+0x220/0x264)
20> [<c025316c>] (dev_deactivate_many+0x220/0x264) from [<c023be04>] (__dev_close_many+0x64/0xd4)
21> [<c023be04>] (__dev_close_many+0x64/0xd4) from [<c023be9c>] (__dev_close+0x28/0x3c)
22> [<c023be9c>] (__dev_close+0x28/0x3c) from [<c023f7f0>] (__dev_change_flags+0x88/0x130)
23> [<c023f7f0>] (__dev_change_flags+0x88/0x130) from [<c023f904>] (dev_change_flags+0x10/0x48)
24> [<c023f904>] (dev_change_flags+0x10/0x48) from [<c024c140>] (do_setlink+0x370/0x7ec)
25> [<c024c140>] (do_setlink+0x370/0x7ec) from [<c024d2f0>] (rtnl_newlink+0x2b4/0x450)
26> [<c024d2f0>] (rtnl_newlink+0x2b4/0x450) from [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4)
27> [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4) from [<c0256740>] (netlink_rcv_skb+0xac/0xc0)
28> [<c0256740>] (netlink_rcv_skb+0xac/0xc0) from [<c024bbd8>] (rtnetlink_rcv+0x18/0x24)
29> [<c024bbd8>] (rtnetlink_rcv+0x18/0x24) from [<c02561b8>] (netlink_unicast+0x13c/0x198)
30> [<c02561b8>] (netlink_unicast+0x13c/0x198) from [<c025651c>] (netlink_sendmsg+0x264/0x2e0)
31> [<c025651c>] (netlink_sendmsg+0x264/0x2e0) from [<c022af98>] (sock_sendmsg+0x78/0x98)
32> [<c022af98>] (sock_sendmsg+0x78/0x98) from [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278)
33> [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278) from [<c022cf08>] (__sys_sendmsg+0x48/0x78)
34> [<c022cf08>] (__sys_sendmsg+0x48/0x78) from [<c0009320>] (ret_fast_syscall+0x0/0x2c)
35
36This patch works around the problem by replacing yield() by msleep(1), giving
37the interrupt thread time to finish, similar to other changes contained in the
38rt patch set. Using wait_for_completion() instead would probably be a better
39solution.
40
41Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
42Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Allen Martin685e0f82016-07-26 19:34:29 -070043---
44 net/sched/sch_generic.c | 2 +-
45 1 file changed, 1 insertion(+), 1 deletion(-)
46
47diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
Ishan Mittalb7998262017-01-17 16:11:50 +053048index 2704a13..3f02edc 100644
Allen Martin685e0f82016-07-26 19:34:29 -070049--- a/net/sched/sch_generic.c
50+++ b/net/sched/sch_generic.c
Allen Martinfc468d82016-11-15 17:57:52 -080051@@ -900,7 +900,7 @@ void dev_deactivate_many(struct list_head *head)
Allen Martin685e0f82016-07-26 19:34:29 -070052 /* Wait for outstanding qdisc_run calls. */
53 list_for_each_entry(dev, head, close_list)
54 while (some_qdisc_is_busy(dev))
55- yield();
56+ msleep(1);
57 }
58
59 void dev_deactivate(struct net_device *dev)
60--
Arvind M10268e72017-12-04 22:18:06 -0800611.9.1
Allen Martin685e0f82016-07-26 19:34:29 -070062