diff mbox series

[17/17] block, bfq: remove unnecessary local variable __bfqq in bfq_setup_merge

Message ID 20230219104309.1511562-18-shikemeng@huaweicloud.com
State New
Headers
Series Some bugfix and cleanup patches for bfq |

Commit Message

Kemeng Shi Feb. 19, 2023, 10:43 a.m. UTC 
  We could traversal bfqq->new_bfqq list without a local variable easily and
intuitively. So remove unnecessary local variable __bfqq.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 block/bfq-iosched.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Comments

Dan Carpenter Feb. 23, 2023, 5:48 a.m. UTC | #1 
Hi Kemeng,

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/block-bfq-properly-mark-bfqq-remained-idle/20230219-104312
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
patch link:    https://lore.kernel.org/r/20230219104309.1511562-18-shikemeng%40huaweicloud.com
patch subject: [PATCH 17/17] block, bfq: remove unnecessary local variable __bfqq in bfq_setup_merge
config: openrisc-randconfig-m041-20230219 (https://download.01.org/0day-ci/archive/20230220/202302200841.9zinyY7i-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202302200841.9zinyY7i-lkp@intel.com/

New smatch warnings:
block/bfq-iosched.c:2785 bfq_setup_merge() error: we previously assumed 'new_bfqq' could be null (see line 2766)

Old smatch warnings:
block/bfq-iosched.c:6195 __bfq_insert_request() warn: variable dereferenced before check 'bfqq' (see line 6191)

vim +/new_bfqq +2785 block/bfq-iosched.c

36eca894832351 Arianna Avanzini 2017-04-12  2751  static struct bfq_queue *
36eca894832351 Arianna Avanzini 2017-04-12  2752  bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
36eca894832351 Arianna Avanzini 2017-04-12  2753  {
36eca894832351 Arianna Avanzini 2017-04-12  2754  	int process_refs, new_process_refs;
36eca894832351 Arianna Avanzini 2017-04-12  2755  
36eca894832351 Arianna Avanzini 2017-04-12  2756  	/*
36eca894832351 Arianna Avanzini 2017-04-12  2757  	 * If there are no process references on the new_bfqq, then it is
36eca894832351 Arianna Avanzini 2017-04-12  2758  	 * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
36eca894832351 Arianna Avanzini 2017-04-12  2759  	 * may have dropped their last reference (not just their last process
36eca894832351 Arianna Avanzini 2017-04-12  2760  	 * reference).
36eca894832351 Arianna Avanzini 2017-04-12  2761  	 */
36eca894832351 Arianna Avanzini 2017-04-12  2762  	if (!bfqq_process_refs(new_bfqq))
36eca894832351 Arianna Avanzini 2017-04-12  2763  		return NULL;
36eca894832351 Arianna Avanzini 2017-04-12  2764  
36eca894832351 Arianna Avanzini 2017-04-12  2765  	/* Avoid a circular list and skip interim queue merges. */
114533e1e26a36 Kemeng Shi       2023-02-19 @2766  	while ((new_bfqq = new_bfqq->new_bfqq)) {
114533e1e26a36 Kemeng Shi       2023-02-19  2767  		if (new_bfqq == bfqq)
36eca894832351 Arianna Avanzini 2017-04-12  2768  			return NULL;
36eca894832351 Arianna Avanzini 2017-04-12  2769  	}

This now loops until new_bfqq is NULL.

36eca894832351 Arianna Avanzini 2017-04-12  2770  
36eca894832351 Arianna Avanzini 2017-04-12  2771  	process_refs = bfqq_process_refs(bfqq);
36eca894832351 Arianna Avanzini 2017-04-12  2772  	new_process_refs = bfqq_process_refs(new_bfqq);

What?

36eca894832351 Arianna Avanzini 2017-04-12  2773  	/*
36eca894832351 Arianna Avanzini 2017-04-12  2774  	 * If the process for the bfqq has gone away, there is no
36eca894832351 Arianna Avanzini 2017-04-12  2775  	 * sense in merging the queues.
36eca894832351 Arianna Avanzini 2017-04-12  2776  	 */
36eca894832351 Arianna Avanzini 2017-04-12  2777  	if (process_refs == 0 || new_process_refs == 0)
36eca894832351 Arianna Avanzini 2017-04-12  2778  		return NULL;
36eca894832351 Arianna Avanzini 2017-04-12  2779  
c1cee4ab36acef Jan Kara         2022-04-01  2780  	/*
c1cee4ab36acef Jan Kara         2022-04-01  2781  	 * Make sure merged queues belong to the same parent. Parents could
c1cee4ab36acef Jan Kara         2022-04-01  2782  	 * have changed since the time we decided the two queues are suitable
c1cee4ab36acef Jan Kara         2022-04-01  2783  	 * for merging.
c1cee4ab36acef Jan Kara         2022-04-01  2784  	 */
c1cee4ab36acef Jan Kara         2022-04-01 @2785  	if (new_bfqq->entity.parent != bfqq->entity.parent)
c1cee4ab36acef Jan Kara         2022-04-01  2786  		return NULL;
c1cee4ab36acef Jan Kara         2022-04-01  2787  
36eca894832351 Arianna Avanzini 2017-04-12  2788  	bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
36eca894832351 Arianna Avanzini 2017-04-12  2789  		new_bfqq->pid);
36eca894832351 Arianna Avanzini 2017-04-12  2790  
36eca894832351 Arianna Avanzini 2017-04-12  2791  	/*
36eca894832351 Arianna Avanzini 2017-04-12  2792  	 * Merging is just a redirection: the requests of the process
36eca894832351 Arianna Avanzini 2017-04-12  2793  	 * owning one of the two queues are redirected to the other queue.
36eca894832351 Arianna Avanzini 2017-04-12  2794  	 * The latter queue, in its turn, is set as shared if this is the
36eca894832351 Arianna Avanzini 2017-04-12  2795  	 * first time that the requests of some process are redirected to
36eca894832351 Arianna Avanzini 2017-04-12  2796  	 * it.
36eca894832351 Arianna Avanzini 2017-04-12  2797  	 *
6fa3e8d34204d5 Paolo Valente    2017-04-12  2798  	 * We redirect bfqq to new_bfqq and not the opposite, because
6fa3e8d34204d5 Paolo Valente    2017-04-12  2799  	 * we are in the context of the process owning bfqq, thus we
6fa3e8d34204d5 Paolo Valente    2017-04-12  2800  	 * have the io_cq of this process. So we can immediately
6fa3e8d34204d5 Paolo Valente    2017-04-12  2801  	 * configure this io_cq to redirect the requests of the
6fa3e8d34204d5 Paolo Valente    2017-04-12  2802  	 * process to new_bfqq. In contrast, the io_cq of new_bfqq is
6fa3e8d34204d5 Paolo Valente    2017-04-12  2803  	 * not available any more (new_bfqq->bic == NULL).
6fa3e8d34204d5 Paolo Valente    2017-04-12  2804  	 *
6fa3e8d34204d5 Paolo Valente    2017-04-12  2805  	 * Anyway, even in case new_bfqq coincides with the in-service
6fa3e8d34204d5 Paolo Valente    2017-04-12  2806  	 * queue, redirecting requests the in-service queue is the
6fa3e8d34204d5 Paolo Valente    2017-04-12  2807  	 * best option, as we feed the in-service queue with new
6fa3e8d34204d5 Paolo Valente    2017-04-12  2808  	 * requests close to the last request served and, by doing so,
6fa3e8d34204d5 Paolo Valente    2017-04-12  2809  	 * are likely to increase the throughput.
36eca894832351 Arianna Avanzini 2017-04-12  2810  	 */
36eca894832351 Arianna Avanzini 2017-04-12  2811  	bfqq->new_bfqq = new_bfqq;
15729ff8143f81 Paolo Valente    2021-11-25  2812  	/*
15729ff8143f81 Paolo Valente    2021-11-25  2813  	 * The above assignment schedules the following redirections:
15729ff8143f81 Paolo Valente    2021-11-25  2814  	 * each time some I/O for bfqq arrives, the process that
15729ff8143f81 Paolo Valente    2021-11-25  2815  	 * generated that I/O is disassociated from bfqq and
15729ff8143f81 Paolo Valente    2021-11-25  2816  	 * associated with new_bfqq. Here we increases new_bfqq->ref
15729ff8143f81 Paolo Valente    2021-11-25  2817  	 * in advance, adding the number of processes that are
15729ff8143f81 Paolo Valente    2021-11-25  2818  	 * expected to be associated with new_bfqq as they happen to
15729ff8143f81 Paolo Valente    2021-11-25  2819  	 * issue I/O.
15729ff8143f81 Paolo Valente    2021-11-25  2820  	 */
36eca894832351 Arianna Avanzini 2017-04-12  2821  	new_bfqq->ref += process_refs;
36eca894832351 Arianna Avanzini 2017-04-12  2822  	return new_bfqq;
36eca894832351 Arianna Avanzini 2017-04-12  2823  }
Kemeng Shi Feb. 23, 2023, 6:34 a.m. UTC | #2 
on 2/23/2023 1:48 PM, Dan Carpenter wrote:
> Hi Kemeng,
> 
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/block-bfq-properly-mark-bfqq-remained-idle/20230219-104312
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
> patch link:    https://lore.kernel.org/r/20230219104309.1511562-18-shikemeng%40huaweicloud.com
> patch subject: [PATCH 17/17] block, bfq: remove unnecessary local variable __bfqq in bfq_setup_merge
> config: openrisc-randconfig-m041-20230219 (https://download.01.org/0day-ci/archive/20230220/202302200841.9zinyY7i-lkp@intel.com/config)
> compiler: or1k-linux-gcc (GCC) 12.1.0
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
> | Link: https://lore.kernel.org/r/202302200841.9zinyY7i-lkp@intel.com/
> 
> New smatch warnings:
> block/bfq-iosched.c:2785 bfq_setup_merge() error: we previously assumed 'new_bfqq' could be null (see line 2766)
> 
> Old smatch warnings:
> block/bfq-iosched.c:6195 __bfq_insert_request() warn: variable dereferenced before check 'bfqq' (see line 6191)
> 
> vim +/new_bfqq +2785 block/bfq-iosched.c
> 
> 36eca894832351 Arianna Avanzini 2017-04-12  2751  static struct bfq_queue *
> 36eca894832351 Arianna Avanzini 2017-04-12  2752  bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
> 36eca894832351 Arianna Avanzini 2017-04-12  2753  {
> 36eca894832351 Arianna Avanzini 2017-04-12  2754  	int process_refs, new_process_refs;
> 36eca894832351 Arianna Avanzini 2017-04-12  2755  
> 36eca894832351 Arianna Avanzini 2017-04-12  2756  	/*
> 36eca894832351 Arianna Avanzini 2017-04-12  2757  	 * If there are no process references on the new_bfqq, then it is
> 36eca894832351 Arianna Avanzini 2017-04-12  2758  	 * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
> 36eca894832351 Arianna Avanzini 2017-04-12  2759  	 * may have dropped their last reference (not just their last process
> 36eca894832351 Arianna Avanzini 2017-04-12  2760  	 * reference).
> 36eca894832351 Arianna Avanzini 2017-04-12  2761  	 */
> 36eca894832351 Arianna Avanzini 2017-04-12  2762  	if (!bfqq_process_refs(new_bfqq))
> 36eca894832351 Arianna Avanzini 2017-04-12  2763  		return NULL;
> 36eca894832351 Arianna Avanzini 2017-04-12  2764  
> 36eca894832351 Arianna Avanzini 2017-04-12  2765  	/* Avoid a circular list and skip interim queue merges. */
> 114533e1e26a36 Kemeng Shi       2023-02-19 @2766  	while ((new_bfqq = new_bfqq->new_bfqq)) {
> 114533e1e26a36 Kemeng Shi       2023-02-19  2767  		if (new_bfqq == bfqq)
> 36eca894832351 Arianna Avanzini 2017-04-12  2768  			return NULL;
> 36eca894832351 Arianna Avanzini 2017-04-12  2769  	}
> 
> This now loops until new_bfqq is NULL.
> 
> 36eca894832351 Arianna Avanzini 2017-04-12  2770  
> 36eca894832351 Arianna Avanzini 2017-04-12  2771  	process_refs = bfqq_process_refs(bfqq);
> 36eca894832351 Arianna Avanzini 2017-04-12  2772  	new_process_refs = bfqq_process_refs(new_bfqq);
> 
> What?Sorry, I didn't expect that there is a behavior change. I will drop
this one in next version. Thanks.
Liu, Yujie March 14, 2023, 8:45 a.m. UTC | #3 
Greeting,

FYI, we noticed maybe_for_address#:#[##] due to commit (built with gcc-11):

commit: 114533e1e26a36efa829659b34941a78b158b613 ("[PATCH 17/17] block, bfq: remove unnecessary local variable __bfqq in bfq_setup_merge")
url: https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/block-bfq-properly-mark-bfqq-remained-idle/20230219-104312
base: https://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git for-next
patch link: https://lore.kernel.org/all/20230219104309.1511562-18-shikemeng@huaweicloud.com/
patch subject: [PATCH 17/17] block, bfq: remove unnecessary local variable __bfqq in bfq_setup_merge

in testcase: blktests
version: blktests-x86_64-f28eb90-1_20230214
with following parameters:

	disk: 1SSD
	test: block-group-07

on test machine: 4 threads Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz (Skylake) with 32G memory

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


If you fix the issue, kindly add following tag
| Reported-by: kernel test robot <yujie.liu@intel.com>
| Link: https://lore.kernel.org/oe-lkp/202303141336.cc6f4cc8-yujie.liu@intel.com


[   96.679266][ T1230] general protection fault, maybe for address 0x7: 0000 [#1] SMP KASAN PTI
[   96.687702][ T1230] CPU: 3 PID: 1230 Comm: dd Not tainted 6.2.0-rc7-00473-g114533e1e26a #1
[   96.695955][ T1230] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.8.1 12/05/2017
[   96.704033][ T1230] RIP: 0010:bfq_setup_merge+0x210/0x460
[   96.709428][ T1230] Code: 00 00 00 fc ff df 48 89 fa 41 0f 95 c5 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ea 01 00 00 <a0> 00 00 00 00 00 fc ff df 44 03 65 04 44 29 e3 44 29 f3 44 29 eb
[   96.728893][ T1230] RSP: 0018:ffffc900028ef5a0 EFLAGS: 00010046
[   96.734815][ T1230] RAX: 0000000000000007 RBX: 0000000000000001 RCX: 00000000fffcd90b
[   96.742646][ T1230] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88880532cb04
[   96.750463][ T1230] RBP: ffff88880532cb00 R08: 1ffff11100f59f7f R09: ffff888802356093
[   96.758284][ T1230] R10: ffffed110046ac12 R11: 0000000000000001 R12: 0000000000000000
[   96.766100][ T1230] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   96.773919][ T1230] FS:  00007f6ad3490580(0000) GS:ffff888791780000(0000) knlGS:0000000000000000
[   96.782694][ T1230] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   96.789124][ T1230] CR2: 000055822213cd38 CR3: 000000025d70c002 CR4: 00000000003706e0
[   96.796943][ T1230] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   96.804762][ T1230] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   96.812583][ T1230] Call Trace:
[   96.815720][ T1230]  <TASK>
[   96.818511][ T1230]  bfq_get_queue+0x736/0xb40
[   96.822953][ T1230]  bfq_get_bfqq_handle_split+0x124/0x5c0
[   96.828434][ T1230]  bfq_init_rq+0x301/0x1780
[   96.832789][ T1230]  ? radix_tree_node_alloc+0x183/0x2c0
[   96.839138][ T1230]  ? elv_merge+0x144/0x3c0
[   96.843405][ T1230]  ? __bfq_insert_request+0x1850/0x1850
[   96.849406][ T1230]  ? _raw_spin_lock_irq+0x86/0xe0
[   96.854279][ T1230]  ? _raw_spin_lock_bh+0xe0/0xe0
[   96.859065][ T1230]  bfq_insert_request+0xdd/0x700
[   96.864458][ T1230]  ? bfq_init_rq+0x1780/0x1780
[   96.869070][ T1230]  ? ioc_find_get_icq+0x195/0x220
[   96.873944][ T1230]  bfq_insert_requests+0x12e/0x220
[   96.878903][ T1230]  ? blk_mq_get_new_requests+0x28e/0x500
[   96.884381][ T1230]  blk_mq_sched_insert_request+0x26d/0x450
[   96.890035][ T1230]  ? blk_mq_sched_bio_merge+0x390/0x390
[   96.895430][ T1230]  ? internal_get_user_pages_fast+0xfa/0x210
[   96.901257][ T1230]  blk_mq_submit_bio+0xb28/0x11d0
[   96.906132][ T1230]  ? copy_page_from_iter_atomic+0x1140/0x1140
[   96.912045][ T1230]  ? blk_mq_try_issue_list_directly+0x310/0x310
[   96.918129][ T1230]  ? find_next_iomem_res+0x239/0x470
[   96.923261][ T1230]  submit_bio_noacct_nocheck+0x481/0x630
[   96.928739][ T1230]  ? should_fail_request+0x70/0x70
[   96.933701][ T1230]  ? __cond_resched+0x20/0x90
[   96.938226][ T1230]  ? bio_add_zone_append_page+0x2b0/0x2b0
[   96.943794][ T1230]  ? get_page_from_freelist+0x6a4/0xc60
[   96.949187][ T1230]  submit_bio_wait+0xfb/0x1f0
[   96.953714][ T1230]  ? __bio_clone+0x300/0x300
[   96.958163][ T1230]  ? bio_iov_iter_get_pages+0xa2/0x250
[   96.963476][ T1230]  ? bio_init+0x31b/0x580
[   96.967663][ T1230]  __blkdev_direct_IO_simple+0x3ef/0x710
[   96.973149][ T1230]  ? __blkdev_direct_IO_async+0x6f0/0x6f0
[   96.978727][ T1230]  ? current_time+0x77/0x220
[   96.983171][ T1230]  ? mode_strip_sgid+0x170/0x170
[   96.987956][ T1230]  ? submit_bio_wait+0x1f0/0x1f0
[   96.992742][ T1230]  ? folio_add_lru_vma+0x74/0xa0
[   96.997530][ T1230]  blkdev_read_iter+0x1f9/0x550
[   97.002230][ T1230]  vfs_read+0x577/0x800
[   97.006237][ T1230]  ? kernel_read+0x130/0x130
[   97.010679][ T1230]  ? __fget_light+0x51/0x220
[   97.015120][ T1230]  ksys_read+0xf1/0x1c0
[   97.019124][ T1230]  ? __ia32_sys_pwrite64+0x1e0/0x1e0
[   97.024258][ T1230]  ? fput+0x1d/0x130
[   97.028004][ T1230]  do_syscall_64+0x39/0x80
[   97.032271][ T1230]  entry_SYSCALL_64_after_hwframe+0x5e/0xc8
[   97.038013][ T1230] RIP: 0033:0x7f6ad33a678e
[   97.042279][ T1230] Code: c0 e9 b6 fe ff ff 50 48 8d 3d ee 04 0b 00 e8 a9 fd 01 00 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 66 0f 1f 84 00 00 00 00 00 48 83 ec 28
[   97.061718][ T1230] RSP: 002b:00007ffd930cfb08 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[   97.069974][ T1230] RAX: ffffffffffffffda RBX: 0000000000001000 RCX: 00007f6ad33a678e
[   97.077794][ T1230] RDX: 0000000000001000 RSI: 000055822213a000 RDI: 0000000000000000
[   97.085616][ T1230] RBP: 000055822213a000 R08: 0000558222139d30 R09: 00007f6ad3489be0
[   97.093436][ T1230] R10: ffffffffffffff3f R11: 0000000000000246 R12: 0000000000000000
[   97.101257][ T1230] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000004
[   97.109078][ T1230]  </TASK>
[   97.111955][ T1230] Modules linked in: null_blk loop dm_multipath dm_mod btrfs ipmi_devintf ipmi_msghandler blake2b_generic xor raid6_pq zstd_compress libcrc32c intel_rapl_msr intel_rapl_common sd_mod t10_pi x86_pkg_temp_thermal crc64_rocksoft_generic intel_powerclamp crc64_rocksoft coretemp crc64 sg kvm_intel i915 kvm irqbypass drm_buddy crct10dif_pclmul intel_gtt crc32_pclmul crc32c_intel drm_display_helper mei_wdt ghash_clmulni_intel ahci ttm sha512_ssse3 rapl libahci wmi_bmof intel_cstate mei_me drm_kms_helper i2c_i801 syscopyarea intel_uncore mei sysfillrect libata video i2c_smbus intel_pch_thermal sysimgblt wmi intel_pmc_core acpi_pad drm fuse ip_tables [last unloaded: null_blk]
[   97.172592][ T1230] ---[ end trace 0000000000000000 ]---
[   97.177897][ T1230] RIP: 0010:bfq_setup_merge+0x210/0x460
[   97.183291][ T1230] Code: 00 00 00 fc ff df 48 89 fa 41 0f 95 c5 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ea 01 00 00 <a0> 00 00 00 00 00 fc ff df 44 03 65 04 44 29 e3 44 29 f3 44 29 eb
[   97.202748][ T1230] RSP: 0018:ffffc900028ef5a0 EFLAGS: 00010046
[   97.208673][ T1230] RAX: 0000000000000007 RBX: 0000000000000001 RCX: 00000000fffcd90b
[   97.216507][ T1230] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88880532cb04
[   97.224335][ T1230] RBP: ffff88880532cb00 R08: 1ffff11100f59f7f R09: ffff888802356093
[   97.232157][ T1230] R10: ffffed110046ac12 R11: 0000000000000001 R12: 0000000000000000
[   97.239977][ T1230] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   97.247798][ T1230] FS:  00007f6ad3490580(0000) GS:ffff888791780000(0000) knlGS:0000000000000000
[   97.256574][ T1230] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   97.263007][ T1230] CR2: 000055822213cd38 CR3: 000000025d70c002 CR4: 00000000003706e0
[   97.270826][ T1230] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   97.278649][ T1230] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   97.286471][ T1230] Kernel panic - not syncing: Fatal exception
[   98.355008][ T1230] Shutting down cpus with NMI
[   98.359536][ T1230] Kernel Offset: disabled


To reproduce:

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        sudo bin/lkp install job.yaml           # job file is attached in this email
        bin/lkp split-job --compatible job.yaml # generate the yaml file for lkp run
        sudo bin/lkp run generated-yaml-file

        # if come across any failure that blocks the test,
        # please remove ~/.lkp and /lkp dir to run from a clean state.
diff mbox series

Patch

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 2705a24ab146..037f73a25567 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2752,7 +2752,6 @@  static struct bfq_queue *
 bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
 {
 	int process_refs, new_process_refs;
-	struct bfq_queue *__bfqq;
 
 	/*
 	 * If there are no process references on the new_bfqq, then it is
@@ -2764,10 +2763,9 @@  bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
 		return NULL;
 
 	/* Avoid a circular list and skip interim queue merges. */
-	while ((__bfqq = new_bfqq->new_bfqq)) {
-		if (__bfqq == bfqq)
+	while ((new_bfqq = new_bfqq->new_bfqq)) {
+		if (new_bfqq == bfqq)
 			return NULL;
-		new_bfqq = __bfqq;
 	}
 
 	process_refs = bfqq_process_refs(bfqq);