Re: [blk] 77c570a1ea: WARNING:at_block/blk-cgroup.c:#blkg_create

[Ammar Faizi]

Adding the committer, reviewer and acker to the CC list. See the full message here:
https://lore.kernel.org/all/20220519070506.GA34017@xsang-OptiPlex-9020/

On 5/19/22 2:05 PM, kernel test robot wrote:
> Greeting,
>
> FYI, we noticed the following commit (built with gcc-11):
>
> commit: 77c570a1ea85ba4ab135c61a028420a6e9fe77f3 ("blk-cgroup: Remove unnecessary rcu_read_lock/unlock()")
> https://github.com/ammarfaizi2/linux-block axboe/linux-block/for-next
>
> in testcase: boot
>
> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
>
> 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 <oliver.sang@xxxxxxxxx>
>
>
>
> [   14.834675][    T1] ------------[ cut here ]------------
> [   14.835078][    T1] WARNING: CPU: 0 PID: 1 at block/blk-cgroup.c:301 blkg_create+0x39/0x513

This hits the `WARN_ON_ONCE(!rcu_read_lock_held());` in the blkg_create(), here:

  https://github.com/ammarfaizi2/linux-block/blob/77c570a1ea85ba4ab135c61a028420a6e9fe77f3/block/blk-cgroup.c#L301


> [   14.835690][    T1] Modules linked in:
> [   14.835984][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc3-00076-g77c570a1ea85 #1
> [   14.836486][    T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014
> [   14.836486][    T1] EIP: blkg_create+0x39/0x513
> [   14.836486][    T1] Code: 89 cb 83 ec 0c 83 05 a0 82 8f d9 01 83 15 a4 82 8f d9 00 e8 a5 be 4c ff 85 c0 75 1e 83 05 a8 82 8f d9 01 83 15 ac 82 8f d9 00 <
> 0f> 0b 83 05 b0 82 8f d9 01 83 15 b4 82 8f d9 00 83 3d 58 9d a6 d8
> [   14.836486][    T1] EAX: 00000000 EBX: f5c26c00 ECX: 00000000 EDX: 00000000
> [   14.836486][    T1] ESI: f5e4c000 EDI: d98f7280 EBP: c12f5e88 ESP: c12f5e70
> [   14.836486][    T1] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010046
> [   14.836486][    T1] CR0: 80050033 CR2: ffd3a000 CR3: 18d38000 CR4: 000406d0
> [   14.836486][    T1] Call Trace:
> [   14.836486][    T1]  ? _raw_spin_lock_irq+0xba/0xe4
> [   14.836486][    T1]  blkcg_init_queue+0xaf/0x20f
> [   14.836486][    T1]  __alloc_disk_node+0x20c/0x3cc
> [   14.836486][    T1]  __blk_alloc_disk+0x55/0x97
> [   14.836486][    T1]  brd_alloc+0x1d9/0x393
> [   14.836486][    T1]  ? debugfs_create_dir+0x20/0x17a
> [   14.836486][    T1]  brd_init+0x12e/0x1f3
> [   14.836486][    T1]  ? ramdisk_size+0x3d/0x3d
> [   14.836486][    T1]  do_one_initcall+0x6f/0x21e
> [   14.836486][    T1]  ? lock_is_held+0x19/0x2b
> [   14.836486][    T1]  ? rcu_read_lock_sched_held+0x4f/0xb7
> [   14.836486][    T1]  do_initcalls+0x17f/0x1ec
> [   14.836486][    T1]  kernel_init_freeable+0x30c/0x3af
> [   14.836486][    T1]  ? rest_init+0x2f7/0x2f7
> [   14.836486][    T1]  kernel_init+0x33/0x2ad
> [   14.836486][    T1]  ret_from_fork+0x19/0x24
> [   14.836486][    T1] irq event stamp: 212188
> [   14.836486][    T1] hardirqs last  enabled at (212187): [<d5163803>] __raw_spin_unlock_irqrestore+0x6e/0xf1
> [   14.836486][    T1] hardirqs last disabled at (212188): [<d70e7620>] _raw_spin_lock_irq+0x5f/0xe4
> [   14.836486][    T1] softirqs last  enabled at (210872): [<d70e9dcb>] __do_softirq+0x463/0x4ed
> [   14.836486][    T1] softirqs last disabled at (210863): [<d50405e3>] call_on_stack+0x20/0x3a
> [   14.836486][    T1] ---[ end trace 0000000000000000 ]---

--
Ammar Faizi