Hi,
On Mon, Nov 19, 2018 at 08:18:24AM -0700, Jens Axboe wrote:
> We need a better way of configuring this, and given that polling is
> (still) a bit niche, let's default to using 0 poll queues. That way
> we'll have the same read/write/poll behavior as 4.20, and users that
> want to test/use polling are required to do manual configuration of the
> number of poll queues.
>
> Reviewed-by: Christoph Hellwig <h...@lst.de>
> Signed-off-by: Jens Axboe <ax...@kernel.dk>
> ---
This patch results in a boot stall when booting parisc (hppa) images
from nvme in qemu.
...
Fusion MPT SAS Host driver 3.04.20
rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
rcu: (detected by 0, t=5252 jiffies, g=141, q=22)
rcu: All QSes seen, last rcu_sched kthread activity 5252 (-66742--71994),
jiffies_till_next_fqs=1, root ->qsmask 0x0
kworker/u8:3 R running task 0 85 2 0x00000004
Workqueue: nvme-reset-wq nvme_reset_work
Backtrace:
[<10190d20>] show_stack+0x28/0x38
[<101dd1e0>] sched_show_task.part.3+0xc4/0x144
[<101dd290>] sched_show_task+0x30/0x38
[<10221e18>] rcu_check_callbacks+0x760/0x7a4
rcu: rcu_sched kthread starved for 5252 jiffies! g141 f0x2 RCU_GP_WAIT_FQS(5)
->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_sched R running task 0 10 2 0x00000000
Backtrace:
[<10995b1c>] __schedule+0x214/0x648
[<10995f94>] schedule+0x44/0xa8
[<1099a7c4>] schedule_timeout+0x114/0x1a0
[<10220e70>] rcu_gp_kthread+0x744/0x968
[<101d5438>] kthread+0x154/0x15c
[<1019501c>] ret_from_kernel_thread+0x1c/0x24
[ continued ]
This is only seen in SMP configurations; non-SMP configurations are ok.
Reverting the patch fixes the problem. v4.20-rcX and earlier kernels
also boot without problems.
For reference, here is the qemu command line. This is with qemu 3.0.
qemu-system-hppa -kernel vmlinux -no-reboot \
-snapshot \
-device nvme,serial=foo,drive=d0 \
-drive file=rootfs.ext2,if=none,format=raw,id=d0 \
-append 'root=/dev/nvme0n1 rw rootwait panic=-1 console=ttyS0,115200 ' \
-nographic -monitor null
Please let me know if you need additional information.
Thanks,
Guenter
