68 lines
3.7 KiB
Diff
68 lines
3.7 KiB
Diff
From 36f709429024a0e49967d177b45571c03ce08224 Mon Sep 17 00:00:00 2001
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Message-Id: <36f709429024a0e49967d177b45571c03ce08224.1601675151.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Marc Kleine-Budde <mkl@pengutronix.de>
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Date: Wed, 5 Mar 2014 00:49:47 +0100
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Subject: [PATCH 033/333] net: sched: Use msleep() instead of yield()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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On PREEMPT_RT enabled systems the interrupt handler run as threads at prio 50
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(by default). If a high priority userspace process tries to shut down a busy
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network interface it might spin in a yield loop waiting for the device to
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become idle. With the interrupt thread having a lower priority than the
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looping process it might never be scheduled and so result in a deadlock on UP
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systems.
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With Magic SysRq the following backtrace can be produced:
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> test_app R running 0 174 168 0x00000000
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> [<c02c7070>] (__schedule+0x220/0x3fc) from [<c02c7870>] (preempt_schedule_irq+0x48/0x80)
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> [<c02c7870>] (preempt_schedule_irq+0x48/0x80) from [<c0008fa8>] (svc_preempt+0x8/0x20)
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> [<c0008fa8>] (svc_preempt+0x8/0x20) from [<c001a984>] (local_bh_enable+0x18/0x88)
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> [<c001a984>] (local_bh_enable+0x18/0x88) from [<c025316c>] (dev_deactivate_many+0x220/0x264)
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> [<c025316c>] (dev_deactivate_many+0x220/0x264) from [<c023be04>] (__dev_close_many+0x64/0xd4)
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> [<c023be04>] (__dev_close_many+0x64/0xd4) from [<c023be9c>] (__dev_close+0x28/0x3c)
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> [<c023be9c>] (__dev_close+0x28/0x3c) from [<c023f7f0>] (__dev_change_flags+0x88/0x130)
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> [<c023f7f0>] (__dev_change_flags+0x88/0x130) from [<c023f904>] (dev_change_flags+0x10/0x48)
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> [<c023f904>] (dev_change_flags+0x10/0x48) from [<c024c140>] (do_setlink+0x370/0x7ec)
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> [<c024c140>] (do_setlink+0x370/0x7ec) from [<c024d2f0>] (rtnl_newlink+0x2b4/0x450)
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> [<c024d2f0>] (rtnl_newlink+0x2b4/0x450) from [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4)
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> [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4) from [<c0256740>] (netlink_rcv_skb+0xac/0xc0)
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> [<c0256740>] (netlink_rcv_skb+0xac/0xc0) from [<c024bbd8>] (rtnetlink_rcv+0x18/0x24)
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> [<c024bbd8>] (rtnetlink_rcv+0x18/0x24) from [<c02561b8>] (netlink_unicast+0x13c/0x198)
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> [<c02561b8>] (netlink_unicast+0x13c/0x198) from [<c025651c>] (netlink_sendmsg+0x264/0x2e0)
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> [<c025651c>] (netlink_sendmsg+0x264/0x2e0) from [<c022af98>] (sock_sendmsg+0x78/0x98)
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> [<c022af98>] (sock_sendmsg+0x78/0x98) from [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278)
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> [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278) from [<c022cf08>] (__sys_sendmsg+0x48/0x78)
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> [<c022cf08>] (__sys_sendmsg+0x48/0x78) from [<c0009320>] (ret_fast_syscall+0x0/0x2c)
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This patch works around the problem by replacing yield() by msleep(1), giving
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the interrupt thread time to finish, similar to other changes contained in the
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rt patch set. Using wait_for_completion() instead would probably be a better
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solution.
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Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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net/sched/sch_generic.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
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index bd96fd261dba..06681749e736 100644
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--- a/net/sched/sch_generic.c
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+++ b/net/sched/sch_generic.c
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@@ -1222,7 +1222,7 @@ void dev_deactivate_many(struct list_head *head)
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/* Wait for outstanding qdisc_run calls. */
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list_for_each_entry(dev, head, close_list) {
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while (some_qdisc_is_busy(dev))
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- yield();
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+ msleep(1);
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/* The new qdisc is assigned at this point so we can safely
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* unwind stale skb lists and qdisc statistics
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*/
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--
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2.17.1
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