Messages in this thread Patch in this message | | | Subject | Re: [LKP] [writeback] 8bc4ad9498: INFO: suspicious RCU usage. ] | From | Jens Axboe <> | Date | Thu, 8 Sep 2016 09:52:46 -0600 |
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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
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