Re: [PATCH] blk-mq: only run mapped hw queues in blk_mq_run_hw_queues()

[Ming Lei <ming.lei@redhat.com>]

On Wed, Mar 28, 2018 at 05:36:53PM +0200, Christian Borntraeger wrote:
> 
> 
> On 03/28/2018 05:26 PM, Ming Lei wrote:
> > Hi Christian,
> > 
> > On Wed, Mar 28, 2018 at 09:45:10AM +0200, Christian Borntraeger wrote:
> >> FWIW, this patch does not fix the issue for me:
> >>
> >> ostname=? addr=? terminal=? res=success'
> >> [   21.454961] WARNING: CPU: 3 PID: 1882 at block/blk-mq.c:1410 __blk_mq_delay_run_hw_queue+0xbe/0xd8
> >> [   21.454968] Modules linked in: scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_mirror dm_region_hash dm_log dm_multipath dm_mod autofs4
> >> [   21.454984] CPU: 3 PID: 1882 Comm: dasdconf.sh Not tainted 4.16.0-rc7+ #26
> >> [   21.454987] Hardware name: IBM 2964 NC9 704 (LPAR)
> >> [   21.454990] Krnl PSW : 00000000c0131ea3 000000003ea2f7bf (__blk_mq_delay_run_hw_queue+0xbe/0xd8)
> >> [   21.454996]            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
> >> [   21.455005] Krnl GPRS: 0000013abb69a000 0000013a00000000 0000013ac6c0dc00 0000000000000001
> >> [   21.455008]            0000000000000000 0000013abb69a710 0000013a00000000 00000001b691fd98
> >> [   21.455011]            00000001b691fd98 0000013ace4775c8 0000000000000001 0000000000000000
> >> [   21.455014]            0000013ac6c0dc00 0000000000b47238 00000001b691fc08 00000001b691fbd0
> >> [   21.455032] Krnl Code: 000000000069c596: ebaff0a00004	lmg	%r10,%r15,160(%r15)
> >>                           000000000069c59c: c0f4ffff7a5e	brcl	15,68ba58
> >>                          #000000000069c5a2: a7f40001		brc	15,69c5a4
> >>                          >000000000069c5a6: e340f0c00004	lg	%r4,192(%r15)
> >>                           000000000069c5ac: ebaff0a00004	lmg	%r10,%r15,160(%r15)
> >>                           000000000069c5b2: 07f4		bcr	15,%r4
> >>                           000000000069c5b4: c0e5fffffeea	brasl	%r14,69c388
> >>                           000000000069c5ba: a7f4fff6		brc	15,69c5a6
> >> [   21.455067] Call Trace:
> >> [   21.455072] ([<00000001b691fd98>] 0x1b691fd98)
> >> [   21.455079]  [<000000000069c692>] blk_mq_run_hw_queue+0xba/0x100 
> >> [   21.455083]  [<000000000069c740>] blk_mq_run_hw_queues+0x68/0x88 
> >> [   21.455089]  [<000000000069b956>] __blk_mq_complete_request+0x11e/0x1d8 
> >> [   21.455091]  [<000000000069ba9c>] blk_mq_complete_request+0x8c/0xc8 
> >> [   21.455103]  [<00000000008aa250>] dasd_block_tasklet+0x158/0x490 
> >> [   21.455110]  [<000000000014c742>] tasklet_hi_action+0x92/0x120 
> >> [   21.455118]  [<0000000000a7cfc0>] __do_softirq+0x120/0x348 
> >> [   21.455122]  [<000000000014c212>] irq_exit+0xba/0xd0 
> >> [   21.455130]  [<000000000010bf92>] do_IRQ+0x8a/0xb8 
> >> [   21.455133]  [<0000000000a7c298>] io_int_handler+0x130/0x298 
> >> [   21.455136] Last Breaking-Event-Address:
> >> [   21.455138]  [<000000000069c5a2>] __blk_mq_delay_run_hw_queue+0xba/0xd8
> >> [   21.455140] ---[ end trace be43f99a5d1e553e ]---
> >> [   21.510046] dasdconf.sh Warning: 0.0.241e is already online, not configuring
> > 
> > Thinking about this issue further, I can't understand the root cause for
> > this issue.
> > 
> > After commit 20e4d813931961fe ("blk-mq: simplify queue mapping & schedule with
> > each possisble CPU"), each hw queue should be mapped to at least one CPU, that
> > means this issue shouldn't happen. Maybe blk_mq_map_queues() works wrong?
> > 
> > Could you dump 'lscpu' and provide blk-mq debugfs for your DASD via the
> > following command?
> 
> # lscpu
> Architecture:        s390x
> CPU op-mode(s):      32-bit, 64-bit
> Byte Order:          Big Endian
> CPU(s):              16
> On-line CPU(s) list: 0-15
> Thread(s) per core:  2
> Core(s) per socket:  8
> Socket(s) per book:  3
> Book(s) per drawer:  2
> Drawer(s):           4
> NUMA node(s):        1
> Vendor ID:           IBM/S390
> Machine type:        2964
> CPU dynamic MHz:     5000
> CPU static MHz:      5000
> BogoMIPS:            20325.00
> Hypervisor:          PR/SM
> Hypervisor vendor:   IBM
> Virtualization type: full
> Dispatching mode:    horizontal
> L1d cache:           128K
> L1i cache:           96K
> L2d cache:           2048K
> L2i cache:           2048K
> L3 cache:            65536K
> L4 cache:            491520K
> NUMA node0 CPU(s):   0-15
> Flags:               esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te vx sie
> 
> # lsdasd 
> Bus-ID     Status      Name      Device  Type  BlkSz  Size      Blocks
> ==============================================================================
> 0.0.3f75   active      dasda     94:0    ECKD  4096   21129MB   5409180
> 0.0.3f76   active      dasdb     94:4    ECKD  4096   21129MB   5409180
> 0.0.3f77   active      dasdc     94:8    ECKD  4096   21129MB   5409180
> 0.0.3f74   active      dasdd     94:12   ECKD  4096   21129MB   5409180

I have tried to emulate your CPU topo via VM and the blk-mq mapping of
null_blk is basically similar with your DASD mapping, but still can't
reproduce your issue.

BTW, do you need to do cpu hotplug or other actions for triggering this warning?

> 
> > 
> > (cd /sys/kernel/debug/block/$DASD && find . -type f -exec grep -aH . {} \;)
> 
> 
> see attachement:

> dasda/range:4
> dasda/capability:10
> dasda/inflight:       0        0
> dasda/ext_range:4
> dasda/power/runtime_suspended_time:0
> dasda/power/runtime_active_time:0
> dasda/power/control:auto
> dasda/power/runtime_status:unsupported
> dasda/dev:94:0

No, it is from sysfs instead of debugfs, so please run the following
command:

	(cd /sys/kernel/debug/block/$DASD && find . -type f -exec grep -aH . {} \;)

Thanks,
Ming