Subject: Re: linux-next: Tree for Aug 1

From: James Bottomley <[email-masked]>
Date: Wed, 01 Aug 2018 17:03:25 -0700

On Thu, 2018-08-02 at 07:57 +0800, Ming Lei wrote:
> On Thu, Aug 2, 2018 at 7:47 AM, Guenter Roeck <[email-masked]>
> wrote:
> > On Wed, Aug 01, 2018 at 03:52:45PM -0700, James Bottomley wrote:
> > > On Wed, 2018-08-01 at 15:48 -0700, Guenter Roeck wrote:
> > > > On Wed, Aug 01, 2018 at 05:58:52PM +1000, Stephen Rothwell
> > > > wrote:
> > > > > Hi all,
> > > > > 
> > > > > Changes since 20180731:
> > > > > 
> > > > > The pci tree gained a conflict against the pci-current tree.
> > > > > 
> > > > > The net-next tree gained a conflict against the bpf tree.
> > > > > 
> > > > > The block tree lost its build failure.
> > > > > 
> > > > > The staging tree still had its build failure due to an
> > > > > interaction
> > > > > with
> > > > > the vfs tree for which I disabled CONFIG_EROFS_FS.
> > > > > 
> > > > > The kspp tree lost its build failure.
> > > > > 
> > > > > Non-merge commits (relative to Linus' tree): 10070
> > > > >  9137 files changed, 417605 insertions(+), 179996 deletions(-
> > > > > )
> > > > > 
> > > > > -----------------------------------------------------------
> > > > > ------
> > > > > -----------
> > > > > 
> > > > 
> > > > The widespread kernel hang issues are still seen. I managed
> > > > to bisect it after working around the transient build failures.
> > > > Bisect log is attached below. Unfortunately, it doesn't help
> > > > much.
> > > > The culprit is reported as:
> > > > 
> > > > 2d542828c5e9 Merge remote-tracking branch 'scsi/for-next'
> > > > 
> > > > The preceding merge,
> > > > 
> > > > 453f1d821165 Merge remote-tracking branch 'cgroup/for-next'
> > > > 
> > > > checks out fine, as does the tip of scsi-next (commit
> > > > 103c7b7e0184,
> > > > "Merge branch 'misc' into for-next"). No idea how to proceed.
> > > 
> > > This sounds like you may have a problem with this patch:
> > > 
> > >     commit d5038a13eca72fb216c07eb717169092e92284f1
> > >      Author: Johannes Thumshirn <[email-masked]>
> > >      Date:   Wed Jul 4 10:53:56 2018 +0200
> > > 
> > >          scsi: core: switch to scsi-mq by default
> > > 
> > > To verify, boot with the additional kernel parameter
> > > 
> > > scsi_mod.use_blk_mq=0
> > > 
> > > Which will reverse the effect of the above patch.
> > > 
> > 
> > Yes, that fixes the problem.
> 
> That may not the root cause, given this issue is only started to
> see from next-20180731, but d5038a13eca7 (scsi: core: switch to
> scsi-mq by default)
> has been in -next for quite a while.
> 
> Seems something new causes this issue.

Read my other email about how to find this.

https://marc.info/?l=linux-scsi&m=153316446223676

Now that we've confirmed the issue, Gunter, could you attempt to bisect
it as that email describes?

Thanks,

James