On Wed, 14 Jul 2021 at 19:22, Naresh Kamboju [off-list ref] wrote:

On Wed, 14 Jul 2021 at 19:01, Greg Kroah-Hartman
[off-list ref] wrote:

quoted

<trim>

My two cents,
While running ssuite long running stress testing we have noticed deadlock.

quoted

So if you drop that, all works well?  I'll go drop that from the queues
now.

Let me drop that patch and test it again.

Crash log,

[ 1957.278399] ============================================
[ 1957.283717] WARNING: possible recursive locking detected
[ 1957.289031] 5.13.2-rc1 #1 Not tainted
[ 1957.292703] --------------------------------------------
[ 1957.298016] kworker/u8:7/236 is trying to acquire lock:
[ 1957.303241] ffff8cc203f92c38 (&bfqd->lock){-.-.}-{2:2}, at:
bfq_finish_requeue_request+0x55/0x500 [bfq]
[ 1957.312643]
[ 1957.312643] but task is already holding lock:
[ 1957.318467] ffff8cc203f92c38 (&bfqd->lock){-.-.}-{2:2}, at:
bfq_insert_requests+0x81/0x1750 [bfq]
[ 1957.327334]
[ 1957.327334] other info that might help us debug this:
[ 1957.333852]  Possible unsafe locking scenario:
[ 1957.333852]
[ 1957.339762]        CPU0
[ 1957.342206]        ----
[ 1957.344651]   lock(&bfqd->lock);
[ 1957.347873]   lock(&bfqd->lock);
[ 1957.351097]
[ 1957.351097]  *** DEADLOCK ***
[ 1957.351097]

Also noticed on stable-rc 5.12.17-rc1.

Reported-by: Linux Kernel Functional Testing <redacted>

ref:
https://lkft.validation.linaro.org/scheduler/job/3058868#L2922

ref:
https://lkft.validation.linaro.org/scheduler/job/3058423#L3125


- Naresh