Re: [PATCH] blk-mq: only run mapped hw queues in blk_mq_run_hw_queues()
From: Christian Borntraeger <hidden>
Date: 2018-03-28 07:45:10
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
On 03/28/2018 05:22 AM, Jens Axboe wrote:quoted hunk ↗ jump to hunk
On 3/27/18 7:20 PM, Ming Lei wrote:quoted
From commit 20e4d813931961fe ("blk-mq: simplify queue mapping & schedule with each possisble CPU") on, it should be easier to see unmapped hctx in some CPU topo, such as, hctx may not be mapped to any CPU. This patch avoids the warning in __blk_mq_delay_run_hw_queue() by checking if the hctx is mapped in blk_mq_run_hw_queues(). blk_mq_run_hw_queues() is often run in SCSI or some driver's completion path, so this warning has to be addressed.I don't like this very much. You're catching just one particular case, and if the hw queue has pending IO (for instance), then it's just wrong. How about something like the below? Totally untested...diff --git a/block/blk-mq.c b/block/blk-mq.c index 16e83e6df404..4c04ac124e5d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c@@ -1307,6 +1307,14 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) int srcu_idx; /* + * Warn if the queue isn't mapped AND we have pending IO. Not being + * mapped isn't necessarily a huge issue, if we don't have pending IO. + */ + if (!blk_mq_hw_queue_mapped(hctx) && + !WARN_ON_ONCE(blk_mq_hctx_has_pending(hctx))) + return; + + /* * We should be running this queue from one of the CPUs that * are mapped to it. *