|
 |
357786 |
From 542fe943f769002a9826f057fcf32acdb1cdc41e Mon Sep 17 00:00:00 2001
|
|
|
357786 |
From: Stefan Hajnoczi <stefanha@redhat.com>
|
|
|
357786 |
Date: Mon, 23 Jul 2018 16:36:29 +0200
|
|
|
357786 |
Subject: [PATCH 89/89] throttle-groups: fix hang when group member leaves
|
|
|
357786 |
|
|
|
357786 |
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
|
|
|
357786 |
Message-id: <20180723163629.7600-2-stefanha@redhat.com>
|
|
|
357786 |
Patchwork-id: 81469
|
|
|
357786 |
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 1/1] throttle-groups: fix hang when group member leaves
|
|
|
357786 |
Bugzilla: 1535914
|
|
|
357786 |
RH-Acked-by: Fam Zheng <famz@redhat.com>
|
|
|
357786 |
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
|
|
|
357786 |
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
|
|
|
357786 |
|
|
|
357786 |
Throttle groups consist of members sharing one throttling state
|
|
|
357786 |
(including bps/iops limits). Round-robin scheduling is used to ensure
|
|
|
357786 |
fairness. If a group member already has a timer pending then other
|
|
|
357786 |
groups members do not schedule their own timers. The next group member
|
|
|
357786 |
will have its turn when the existing timer expires.
|
|
|
357786 |
|
|
|
357786 |
A hang may occur when a group member leaves while it had a timer
|
|
|
357786 |
scheduled. Although the code carefully removes the group member from
|
|
|
357786 |
the round-robin list, it does not schedule the next member. Therefore
|
|
|
357786 |
remaining members continue to wait for the removed member's timer to
|
|
|
357786 |
expire.
|
|
|
357786 |
|
|
|
357786 |
This patch schedules the next request if a timer is pending.
|
|
|
357786 |
Unfortunately the actual bug is a race condition that I've been unable
|
|
|
357786 |
to capture in a test case.
|
|
|
357786 |
|
|
|
357786 |
Sometimes drive2 hangs when drive1 is removed from the throttling group:
|
|
|
357786 |
|
|
|
357786 |
$ qemu ... -drive if=none,id=drive1,cache=none,format=qcow2,file=data1.qcow2,iops=100,group=foo \
|
|
|
357786 |
-device virtio-blk-pci,id=virtio-blk-pci0,drive=drive1 \
|
|
|
357786 |
-drive if=none,id=drive2,cache=none,format=qcow2,file=data2.qcow2,iops=10,group=foo \
|
|
|
357786 |
-device virtio-blk-pci,id=virtio-blk-pci1,drive=drive2
|
|
|
357786 |
(guest-console1)# fio -filename /dev/vda 4k-seq-read.job
|
|
|
357786 |
(guest-console2)# fio -filename /dev/vdb 4k-seq-read.job
|
|
|
357786 |
(qmp) {"execute": "block_set_io_throttle", "arguments": {"device": "drive1","bps": 0,"bps_rd": 0,"bps_wr": 0,"iops": 0,"iops_rd": 0,"iops_wr": 0}}
|
|
|
357786 |
|
|
|
357786 |
Reported-by: Nini Gu <ngu@redhat.com>
|
|
|
357786 |
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
|
|
|
357786 |
Message-id: 20180704145410.794-1-stefanha@redhat.com
|
|
|
357786 |
Cc: Alberto Garcia <berto@igalia.com>
|
|
|
357786 |
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
|
|
|
357786 |
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
|
|
|
357786 |
---
|
|
|
357786 |
block/throttle-groups.c | 4 ++++
|
|
|
357786 |
1 file changed, 4 insertions(+)
|
|
|
357786 |
|
|
|
357786 |
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
|
|
|
357786 |
index 36cc043..e297b04 100644
|
|
|
357786 |
--- a/block/throttle-groups.c
|
|
|
357786 |
+++ b/block/throttle-groups.c
|
|
|
357786 |
@@ -564,6 +564,10 @@ void throttle_group_unregister_tgm(ThrottleGroupMember *tgm)
|
|
|
357786 |
|
|
|
357786 |
qemu_mutex_lock(&tg->lock);
|
|
|
357786 |
for (i = 0; i < 2; i++) {
|
|
|
357786 |
+ if (timer_pending(tgm->throttle_timers.timers[i])) {
|
|
|
357786 |
+ tg->any_timer_armed[i] = false;
|
|
|
357786 |
+ schedule_next_request(tgm, i);
|
|
|
357786 |
+ }
|
|
|
357786 |
if (tg->tokens[i] == tgm) {
|
|
|
357786 |
token = throttle_group_next_tgm(tgm);
|
|
|
357786 |
/* Take care of the case where this is the last tgm in the group */
|
|
|
357786 |
--
|
|
|
357786 |
1.8.3.1
|
|
|
357786 |
|