lkml.org 
[lkml]   [2016]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [LKP] [writeback] 8bc4ad9498: INFO: suspicious RCU usage. ]
From
Date
On 09/07/2016 08:04 PM, Ye Xiaolong wrote:
> On 09/08, Fengguang Wu wrote:
>> Hi Jens and Tejun,
>>
>>> The command line was in the original email:
>>>
>>> $ qemu-system-x86_64 -enable-kvm -cpu Westmere -m 512M
>>>
>>> And agree, in general it'd be nice if there was a link to the image as
>>> well, so that folks can reproduce.
>>
>> Yes we have a reproduce script internally, however need to polish it
>> up and make it general usable by kernel developers.
>>
>> CC Philip. It'd be helpful to give more priority to the "lkp qemu"
>> reproduce command.
>>
>> For the warning here, it does not depend on any initrd, I just
>> confirmed this simple script can reproduce the problem.
>
> Yes, just confirmed that v4.8-rc5 doesn't have this warning, while kernel
> for the updated commit (fa0e2cb1af765691fabd329f03cad563a0eebf18) on branch
> wb-buf-throttle could reproduce it.

Anyone willing to try the below patch?

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ef61bda76317..a7bb2e6bcaef 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3764,9 +3764,11 @@ static void check_blkcg_changed(struct cfq_io_cq
*cic, struct bio *bio)
struct cfq_data *cfqd = cic_to_cfqd(cic);
struct cfq_queue *cfqq;
uint64_t serial_nr;
+ bool nonroot_cg;

rcu_read_lock();
serial_nr = bio_blkcg(bio)->css.serial_nr;
+ nonroot_cg = bio_blkcg(bio) != &blkcg_root;
rcu_read_unlock();

/*
@@ -3781,7 +3783,7 @@ static void check_blkcg_changed(struct cfq_io_cq
*cic, struct bio *bio)
* do proper throttling of writes. Turn off wbt for that
* case.
*/
- if (bio_blkcg(bio) != &blkcg_root) {
+ if (nonroot_cg) {
struct request_queue *q = cfqd->queue;

if (q->rq_wb)
--
Jens Axboe

\
 
 \ /
  Last update: 2016-09-17 09:58    [W:0.054 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site