On Dec 8, 2018, at 11:22 PM, Guenter Roeck <li...@roeck-us.net> wrote: > >> On 12/8/18 9:38 PM, Jens Axboe wrote: >>> On 12/8/18 5:49 PM, Guenter Roeck wrote: >>> 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. >> Hmm, I think the queue reduction case has a logic error. Actually there >> are two bugs: >> 1) Ensure we don't keep overwriting the queue count we ask for >> 2) Don't include poll_queues in the vectors we need >> Untested... And not super pretty. But does this work for you? > > It solves the boot problem on parisc/hppa. I didn't test with any other > architectures. > Should I run a complete test sequence ?
That’d be great, thanks.