Re: linux-next: Tree for Aug 1

From: Guenter Roeck
Date: Wed Aug 01 2018 - 20:13:39 EST

On 08/01/2018 04:57 PM, Ming Lei wrote:
On Thu, Aug 2, 2018 at 7:47 AM, Guenter Roeck <linux@xxxxxxxxxxxx> 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
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 <jthumshirn@xxxxxxx>
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


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.

Agreed. I should have said "fixes the symptom". I'll try to bisect
with scsi_mod.use_blk_mq=1 as suggested by James.